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###### ###### Issue #7
################## Feb. '94
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-----------------------------------------------------------------------------
Editor's Notes:
by Craig Taylor (duck@pembvax1.pembroke.edu)
This net-magazine is still alive after over two years suprising even
myself. There should be more to come also!! And it's been late everytime
it's been released. :-) I dunno - I'm trying not to make that a
tradition but next time I don't think I'm going to set any firm dates so
it can't possibly be late.
Lesee, first to address some questions and queries that have been going
on over the network:
- The C project that I mentioned a while back is now officially
defunct, dead, resting in peace... whatever you want to call it.
There may be other individuals working on their own version of an
ANSI C compiler but the group that was setup is no longer.
Basically, it was a problem of too many programmers, too few
managers (and we know programmers *grins* - They all want to do it
their way. Incidentilly - my way _was_ the best. ;-) )
- The C65 exists but there are very few of them out there and
GrapeVine no longer sells them (out of stock I believe). It was only
made in small quantities for prototype work. There have been
numerous individuals reading comp.sys.cbm that see mention of the
C65 and assume that this creature Commodore released. Commodore sold
a warehouse and its contents to Grapevine and Grapevine stumbled
across them and sold 'em. They are functional but due to the low
number of them available I doubt that there will be any C65 targated
applications. (Someone prove me wrong, please?)
- Geesh - That stupid article about the 1351 mouse that I kept
promising from issue 2 on I've officially declared dead. It may come
around later but for now it's dead. It's existed as a promise in one
form or another since issue 2 so this message officially kills it.
- Also there was some confusion last time about my wording about not
writing any more articles and such (or rather, not as many as I had
been). Basically, yes - I'm still going to do C=Hacking - it's just
that because of time, frustration, school and jobs that I don't have
as much time to devote to researching and writing articles. That's
all that I meant to say - some people were concerned that C=Hacking
was no longer going to be released...
As always, here's the obligatory begging for authors on any type of
software or hardware project that involves the Commodore computers.
Please, Please if you or your user group has any information or material
concerning the Commodore computers that you think may be appropriate for
C=Hacking let me know via e-mail at duck@pembvax1.pembroke.edu. I'm
looking for anything from hardware schematic, programming theory to
actual programming techniques, programs.
The articles in this issue of C=Hacking I'm especially pleased with.
There are two articles concerning the VIC chip and its operations that
detail how certain "magical" techniques are performed. Also, Marko
Makela has written a very detailed, interesting article on various
memory techniques for the C-64. We also have a summary of the ACE
programming / operating system and a referance guide on how to write
applications for it. I've also included an InterNet guide that I've
started writing to show individuals how to use the InterNet to get
Commodore-64/128/Vic-20 related material. Included within that is a list
of FTP sites containing numerous programs.
=============================================================================
Please note that this issue and prior ones are available via anonymous
FTP from ccosun.caltech.edu (among others) under pub/rknop/hacking.mag
and via a mailserver which documentation can be obtained by sending
mail to "duck@pembvax1.pembroke.edu" with a subject line of
"mailserver" and the line "help" in the body of the mesage.
=============================================================================
NOTICE: Permission is granted to re-distribute this "net-magazine", in
whole, freely for non-profit use. However, please contact individual
authors for permission to publish or re-distribute articles
seperately. A charge of no greater than 5 US dollars or equivlent may
be charged for library service / diskette costs for this
"net-magazine".
=============================================================================
In This Issue:
Commodore Trivia Corner
This section of C=Hacking will contain numerous questions that will test
your knowledge of trivia for the Commodore computers. Each issue they'll
be answers to the previous issues questions and new questions. How much
do you know?
InterNet Resources for the Commodore 64 / 128 V1.0
This article goes into detail about the available resources on the InterNet
and is meant to introduce people to the wonderful, wacky world of the
InterNet. It covers what the InterNet is, what capabilities it has and
how to access those capabilities. In addition, it also includes Howard
Herman's latest list of File Transfer sites for the Commodore computers.
Hiding kilobytes
Most Commodore 64 programs do not utilize even nearly all of the 64 kB
random access memory space. By default, there are only 44 kilobytes of
accessible RAM. This article describes how you can take the hiding 20
kilobytes to use.
FLD - Scrolling the Screen
This article, using a technique described by Pasi Ojala in the last
issue of C=Hacking, gives an example of a program using Flexible Line
Distance technique.
Tech-tech - more resolution to vertical shift
At one time half of the demos had pictures waving horizontally on the width
of the whole screen. This effect is named tech-tech and it is done using
character graphics. How exactly and is the same possible with sprites ?
ACE-128/64 PROGRAMMER'S REFERENCE GUIDE (version 0.9, for Release #10)
This article explains the complete system interface for the ACE-128/64
computing environment. It is intended to be used by programmers for
developing software to run on top of the ACE kernel. ACE is a program
for the Commodore 128 and Commodore 64 that provides a command shell
environment that is similar to that of Unix.
===============================================================================
Commodore Trivia Corner
by Jim Brain (brain@mail.msen.com)
Everyone who reads this article has had, or presently owns a Commodore
computer of some kind. I own more than one, which is not uncommon among
Commodore enthusiasts. Well, I bought my first Commodore computer in
1982, a brand new Vic-20 with some game cartridges. I had wanted an
Atari, but father knew best and he told the then 11 year old son that
computers would shape my life more than any game machine. Well, it is
11 years later and a Computer Engineering Degree earned, and I have
spent many a night during that time playing on many models of Commdore
equipment. Now, I would like to share the knowledge I have with you in
an interesting way.
As you now know a little about me, let us see how much you know about
the machines and company that binds us all together. The following is
an installment of Commodore Trivia. These questions have been gleaned
from books, magazines, persoanl knowledge, work on the machines in
questions, and other fellow commodore users happy to share interesting
bits of semi- useless knowledge concerning the CBM systems.
This installment consists of two parts, the December 1993 edition
complete with answers and the January 1994 edition without answers.
Each new issue of Commodore Hacking Magazine will contain more
questions, as well as answers to the previous issue's questions. Each
new edition is also posted every month on the 12th of the month on the
Usenet newsgroup comp.sys.cbm. Winners will be announced on the
newsgroup, and prizes may be awarded. For anyone wishing to submit
answers from this article, please email your responses with question
numbers preceeding each answer to :
brain@msen.com
The answers to this edition will be posted on the 12th of February in
comp.sys.cbm with the next edition of questions. Have fun trying to
answer the questions and feel free to send me a note with new questions.
I can always use them.
[Ed's Note: In addition, the mailserver that I have setup for
C=Hacking will make provisions to allow individuals to retrieve the
newest set of questions and last month's answers. Currently not
implemented, it should be available soon. Details in the next issue.
Also due to C= Hacking being published fairly irregularly and not
every month the column here will contain answers to the last issue of
C=Hacking's questions and have new questions for the month that it's
released in.]
-----------------------------------------------------------------------------
Here are the answers to the 10 questions in Commdore Triva Edition #1 for
December 1993. [that were posted on comp.sys.cbm]
Q $000) Commodore started out into computing with the PET series of
computers. I am not sure if the first ones had PET emblem, but
nonetheless, What does P E T stand for?
A $000) Personal Electronic Transactor
Since the acronym was made up before the expansion, the following
are also valid:
Personal Electronic Translator
Peddle's Ego Trip
Q $001) Commodore planned to manufacture a successor series to the
successful Commodore 64 home computer. Both were intended to
be Business machines. We all know this resulted in the Commodore
Plus 4, but what were the machines originally called and what was
the difference between the two?
A $001) the 364, which had, among other things, a larger Plus 4 style case
that housed the regular keyboard plus a numeric keypad. the 264
turned into the Plus 4, with 64K of RAm. We will never know much
more about the 364, since it got scrapped.
Q $002) How much free memory does a Vic-20 have (unexpanded)?
A $002) Oooh! There are many answers for this.
The VIC has 3583 bytes of RAM for BASIC
The VIC has 4096 bytes of RAM for ML
The VIC has 5120 bytes of RAM. 4K of RAM + 1K for Video.
Q $003) What early 80's Commodore software company had a Light Bulb
as a company logo?
A $003) Skyles Electric Works.
The Vic-20 came out with a few peripherals I want the model
numbers for the :
Q $004) Disk Drive
A $004) VIC-1540 - Same as 1541, only faster serial spped.
Q $005) Cassette Player
A $005) VIC-1530
Q $006) Printer
A $006) VIC 1515, which, by a miscommunication, could only use 7.5" paper.
Evidently, someone thought 8.5" meant full width of paper w/ perfs!
This printer was quickly supplanted and overtaken by the 1525, which
should own this title in the first place!
Q $007) 16 K Ram Expansion.
A $007) VIC-1111
Q $008) Commodore Introduced 3 printers that used the same printer mechanism.
What are the model numbers.
A $008) MPS 802 (Square Dots, Serial), CBM 1526 (Round Dots, Serial),
PET 4023 (Round Dots, IEEE-488).
Q $009) What is the diferences between the printers in #9
A $009) MPS 802 (Square Dots, Serial), CBM 1526 (Round Dots, Serial),
PET 4023 (Round Dots, IEEE-488).
-----------------------------------------------------------------------------
Here are the questions for Commodore Trivia Edition #2 for January 1994.
Q $00A) What was the Code-Name of the Amiga while in Development?
Q $00B) What is Lord British's Real Name (The creator of the Ultima
Series)?
Q $00C) What is the POKE location and value that will fry an early model
PET?
Q $00D) On the Plus 4 and C-16, the VIC chip was replaced with the TED
chip. What does TED stand for?
Q $00E) Commodore Produced a Letter Quality Printer in North America
(maybe elsewhere) for the Commdore Serial Line. Name it.
Q $00F) What is the version of DOS in the 1541?
Q $010) What is the Version of BASIC in the Plus 4 and the C-16?
Q $011) What are the nicknames of the original three custom Amiga chips?
Q $012) Commodore produced a 64 in a PET case. What is its name and model
number?
Q $013) Commodore sold a 1 megabyte floppy disk drive in a 1541 case.
Give the model number.
Q $014) What does GCR stand for?
Q $015) Commdore produced a drive to accompany the Plus 4 introduction.
Give the model number.
Q $016) What does SID stand for?
Q $017) What does the acronym KERNAL stand for?
Q $018) What version of DOS does the 1571 have?
Q $019) What other two Commdore Disk Drives share the same DOS version
number as the 1571?
Q $01A) How many files will the 1571 hold?
Q $10B) How many files will the 1541 hold?
Q $01C) What did Commodore make right before entering the computer market?
Q $01D) Commodore introduced an ill-fated 4 color plotter. Give the model
number.
Q $01E) Some formats of CP/M write disks using the MFM format. What does
MFM stand for?
Q $01F) On the Commodore 128, the user manual left two commands undocumented.
One works, and the other gives a not-implemented error. Name both
commands and what each one does or does not do.
Some are easy, some are hard, try your hand at it.
Jim Brain
brain@msen.com
=============================================================================
InterNet Resources for the Commodore 64 / 128 V1.0
by Craig Taylor (duck@pembvax1.pembroke.edu)
[This article is placed into public domain by the author. Copying encouraged]
The Internet
Let me start this article with a quote by another author that everyone
should heed when dealing with the InterNet:
"One warning is perhaps in order---this territory we are entering can
become a fantastic time-sink. Hours can slip by, people can come and
go, and you'll be locked into Cyberspace. Remember to do your work!
With that, I welcome you, the new user, to The Net."
brendan@cs.widener.edu
- Author, Zen and the Art of the Internet
What is the InterNet?
What exactly is the InterNet? Imagine if you will, when you were a kid
stringing wires between houses in your neighborhood so that you could
talk with the kids that lived beside you. You could talk to those beside
you but not the ones that lived across town. Now, suppose that you
wanted to relay a message to a buddy across town. The only feasible way
would be to send a message to the guy next door; then have him send it
to the correct person.
This is the basic system of the Internet. Computers connected to other
computers that are connected to others. In the above paragrph
communication was limited because of geography - how close individuals
were. The InterNet system; while geography does play a factor, relies
more on how the sites grew up and were established as to how messages
will get passed back and forth.
There are also other networks hooked up to the InterNet that provide
auxilary services to their local group of computers. One large one is
BITNET and UUCP. Various bbs's also carry items from the InterNet such
as the BitNet news. In addition, online services such as Genie,
Compuserve, and others offer "gate-ways" or ways of getting access to
the resources of the InterNet.
Access To The InterNet
Gaining Access to the InterNet There are several ways of gaining access
to the InterNet. Your local college may be your best low-cost
opportunity. Typically, if you are a student or faculty or staff, you
may qualify to have an account that allows you to access all the
InterNet facilities described above. If you don't fall into any of these
categories your next best bet is an online service such as America
Online, Genie, or Compuserve as these all support what is known as an
InterNet gateway - allowing you t o access the InterNet through t hem.
(At this time, I don't believe Prodigy has an InterNet gateway - if I'm
wrong I'm sure I'll get tons of mail. Other online services also exist -
I've only listed what I consider the "primary" ones.)
Once you've gotten access to the InterNet you may be asking "Okay, I
know what the InterNet _can_ give me - how do I do it?" Unfortunately,
because the InterNet is run on differant computer systems this will vary
from system to system. Your best bet would be to examine the
documentation and help screens associated with the online service or
college's facilities. Study them over until you can quote them backwards
(well, not quite that much) - Study them over until you understand what
they are saying. Also, having someone who is already experienced with
the InterNet aid you in your explorations is a great help.
What is E-MAIL?
There are numerous individuals using the InterNet each day. Each is also
able to write the other through the use of Electronic Mail or, as it's
commonly called "e-mail".
To send a message to me you'd use your mail program (the actual
procedure varies depending on what type of machine you use) and tell it
to send the message to my user name, "duck" at my site that I login at -
(currently going to Pembroke State University) hence
"pembvax1.pembroke.edu". So the full address with an "@" sign the
computer needs to use to know how to seperate the computer name and the
user name is "duck@pembvax1.pembroke.edu".
It's easy to talk to somebody in Mexico, Germany, Australia with this
method and it's quicker than the U.S. Postal system (which, on the
InterNet you'll see referred to as Snail Mail (or s-mail) due to it's
slow delivery time compared to e-mail). Projects, Questions, Answers,
Ideas and general chit-chat on how the family is doing, etc can be
relayed over the InterNet.
There are also numerous abbreviations and notations that are used in
E-Mail. Some of them are:
ttyal8r - Talk to you later
rtfm - Read the *uckin' manual
imho - In My Humble Opinion
rotfl - Rolls on the Floor Laughing
lol - Laughs Out Loud.
l8r - Later
;-) - (winks)
:-) - (smile)
:-( - (frowns)
There are _many_ _many_ more - you can also find a huge list of the
smiley faces (turn your head sideways and look at the ones in
parenthesis above) on the InterNet.
You may also hear the phrase "my e-mail bounced". What this means is
that your message, much like a bounced check, did not work right and it
was returned to your account. Typically this happens because of
incorrect addresses, or an incorrect user name.
Email Servers
Another large way of getting information is from individuals running
what are E-Mail servers from their accounts or from specific accounts.
From Email servers you may request certain files; catalogs of programs
that are availble for request; send messages to be distributed to other
individuals and automatically subscribe yourself to the mailing list for
new items.
The only Email Server specifically designed for the Commodore computers
is one ran by the author. It major intent is that of distributing the
Commodore Hacking magazine as well as programs that are in the
magazine. To get help on how to use it send a message to the author in
the following format:
To: duck@pembvax1.pembroke.edu
Subj: MAILSERV
Body of message: HELP
This specific mailserver is ran twice a day so you should get your reply
within approximately 12 hours. Please be sure to have a subject line of
"MAILSERV".
If anyone knows of any other Email Servers existing for the Commodore
computers please let the author know.
NewsGroups
One of the primary purposes of the InterNet is for educational research
and discussion. For this purpose, there are currently over 2000
newsgroups established dealing with a wide range of social, politicial,
science, computer and educational topics. Some of these range to inane,
whimsical, to practical and useful.
Two of these for the Commodore 64/128 line of computers are:
comp.sys.cbm
comp.binaries.cbm
The names for the newsgroups start with a short abbreviation such as
"comp" for computers, "sci" for science, "bio" for biology, etc... The
second group of letters stand for the type of newsgroup "sys for system,
binaries for binaries etc..." while the third describes it better -
"cbm" in this case for Commodore Business Machines.
The newsgroup, Comp.Sys.Cbm supports discussion about anything under the
sun involving the Commodore 8 bit line of computers (and lately, even
talking about the old old ancient calculators that Commodore mae that
might not have even been 8 bit). Comp.Binaries.Cbm allows programs to be
"posted" or made available to everyone who wishes them. There are
programs available that will let you take the "encrypted" text-only
version of the program that you see on the screen and convert them into
the correct binary p rogram.
Basically the rules for newsgroups are: 1) Enjoy yourself, 2) Don't
harass others and 3) Try to stay on topic. Newsgroups are read by many
many people - typically you'll get a response to an inquiry within only
an hour or so - sometimes even sooner. But because they're read by so
many people chatter or "babble" as it's known, is also discouraged.
Don't hesitate to post any questions, concerns or comments but make sure
in each message that you post that you have a reason to post.
So What's Out There?
So why should you be interested in the Internet? Imagine, if you will,
being able to ask questions to numerous individuals, download the latest
in shareware and public-domain software, know the "rumours" and topics
before they exist all for free? (Or at least, only for what your
"hookup" method charges - see Gaining Access to the InterNet latter).
That's what's out on the Internet. Any question you have - there is sure
to be an answer for - any software you're looking for you stand an
extremely good chance of finding something along the lines of your
needs.
The major benefit of the Internet as I see it consists of the continued
support for the Commodore computers. Because all these differant means
of obtaining information are not sponsored by any one specific company
or individual the Commodore 8-bit line of computers are guranteed
continued support over the Internet. In addition, because the Internet
strongly frowns upon Commercial advertising you won't find numerous ads
or any other material urging you to "buy this, buy that" like you will
on some other serv ices.
FTP Sites
FTP stands for File Transfer Protocols and is a method of obtaining
programs that are stored on another system's computers. There are
numerous FTP sites out there in InterNet land - one of the best
currently available for the Commodore computers is that of R.Knop's site
at ccosun.caltech.edu.
[ The following is a list of FTP sites for the Commodore 64 and 128
computes and is currenty maintained by Howard Herman
(h.herman@GEnie.geis.com) and is used with his permission. He usually
posts an updated list to comp.sys.cbm newsgroup every month or so.]
-----------------------------------------------------------------------------
This is the list of FTP sites containing software and programs
specific to the Commodore 64 and 128 computers.
I will try to keep this list as current and accurate as possible, so
that it can be a useful resource for users of the newsgroup.
PLEASE cooperate and send E-mail to me with any corrections and
updates. If a site has closed or no longer carries CBM software, let
me know and it will be deleted. If you uncover a site not listed,
tell me so that it can be added.
-----
To use this list on a UNIX system, just type 'ftp <sitename>', where
<sitename> is any of the sites listed below. Use 'anonymous' as
your login, and your E-mail address for the password. You can change
and list directories with 'cd' and 'dir', respectively, and download
files to your system using 'get'. Be sure to specify either 'binary'
if you are getting a program, or 'ascii' for a text file before you
begin the download.
-----
In addition to the sites listed below there are hundreds of other
FTP sites on INet with interesting files covering every topic
imaginable. Take some time to seek out and explore these too.
Enjoy!
-----
Host sol.cs.ruu.nl (131.211.80.17)
Last updated 00:39 4 Sep 1993
Location: /pub/MIDI/PROGRAMS
DIRECTORY rwxr-xr-x 1024 Aug 26 09:58 C64
Location: /pub/MIDI/DOC
FILE rw-r--r-- 40183 Jan 19 1993 C64midi-interface.txt
Host uceng.uc.edu (129.137.33.1)
Last updated 04:38 6 Sep 1993
Location: /pub/wuarchive/systems/cpm/c128
FILE rw-r--r-- 24576 Nov 6 1986 c128-mex.com
Location: /pub/wuarchive/systems/cpm/c64
FILE rw-r--r-- 1615 Mar 14 1984 c64-cpm.msg
FILE rw-r--r-- 1536 Feb 9 1985 c64modem.com
FILE rw-r--r-- 4199 Feb 10 1984 c64modem.doc
FILE rw-r--r-- 19200 Feb 9 1985 md730c64.com
FILE rw-r--r-- 2192 Oct 1 1984 md730c64.doc
Location: /pub/wuarchive/doc/misc/if-archive/infocom/tools
FILE r--r--r-- 5798 Aug 5 14:42 c64todat.tar.Z
Host aix370.rrz.uni-koeln.de (134.95.80.1)
Location: /.disk2/usenet/comp.archives/auto/comp.sys.cbm
DIRECTORY rwxrwxr-x 384 comp.sys.cbm
Host ftp.csv.warwick.ac.uk (137.205.192.5)
Last updated 00:00 18 Jan 1994
Location: /pub/c64
FILE rw-r--r-- 909 Jan 8 19:52 C64progs.doc
FILE rw-r--r-- 19558 Jan 8 19:49 backgamm.sfx
FILE rw-r--r-- 21384 Jan 8 19:49 chequebo.sfx
FILE rw-r--r-- 11449 Jan 8 19:49 countdow.sfx
FILE rw-r--r-- 18136 Jan 8 19:49 draughts.sfx
FILE rw-r--r-- 5011 Jan 8 19:49 loader.sfx
FILE rw-r--r-- 17423 Jan 8 19:49 whitewas.sfx
Descriptions:
============
backgamm - Backgammon board game
chequebo - Cheque Book Organiser, written in basic with UK pound sign as
currency, but could be changed to suit another.
countdow - LOAD"count example",8,1 and watch the countdown during loading.
draughts - Draughts board game.
loader - Press RESTORE key and MENU on disk will be automatically re-loaded.
whitewas - Colour squares board game.
Location: /tmp/c64
>Temporary files stored here. If /tmp directory not found, try
>again at another time. /tmp directory not always available.
Host clover.csv.warwick.ac.uk (137.205.192.6)
Last updated 13:29 27 Sep 1993
Location: /pub/c64
FILE rw-r--r-- 812 c64progs.doc
FILE rw-r--r-- 73696 c64progs.sfx
Host nexus.yorku.ca (130.63.9.66)
Last updated 00:00 21 Dec 1993
Location: /pub/Internet-info
FILE rw-r--r-- 6308 commodore.ftp
>An older version of this listing.
Host rigel.acs.oakland.edu (141.210.10.117)
Last updated 01:42 3 Sep 1993
Location: /pub2/cpm
DIRECTORY rwxr-xr-x 1536 Jun 4 1992 c128
DIRECTORY rwxr-xr-x 512 c64
Location: /pub2/cpm/c64
FILE rw-r--r-- 1615 Mar 14 1984 c64-cpm.msg
FILE rw-r--r-- 1536 Feb 9 1985 c64modem.com
FILE rw-r--r-- 4199 Feb 10 1984 c64modem.doc
FILE rw-r--r-- 19200 Feb 9 1985 md730c64.com
FILE rw-r--r-- 2192 Oct 2 1984 md730c64.doc
Host oak.oakland.edu
Last updated 00:00 18 Dec 1993
Location: /pub2/cpm
>For CP/M software, most all of which will run on the C128.
Host src.doc.ic.ac.uk (146.169.2.1)
Location: /usenet/comp.archives/auto
DIRECTORY rwxr-xr-x 512 comp.sys.cbm
Location: /usenet/comp.archives
DIRECTORY rwxr-xr-x 512 commodore-64-128
DIRECTORY rwxr-xr-x 512 May 3 1991 c64
Location: /media/visual/collections/funet-pics/jpeg/games
DIRECTORY rwxr-xr-x 512 Mar 20 05:48 c64
Location: /media/visual/collections/funet-pics/jpeg/comp/games
DIRECTORY rwxr-xr-x 512 May 6 03:55 c64
Host tupac-amaru.informatik.rwth-aachen.de (137.226.112.31)
Last updated 04:59 7 Oct 1992
Location: /pub/rz.archiv/simtel/cpm
DIRECTORY rwxr-xr-x 512 c64
DIRECTORY rwxr-xr-x 512 Sep 21 20:56 c128
Host wuarchive.wustl.edu (128.252.135.4)
Last updated 02:40 23 May 1993
Location: /systems/amiga/incoming/misc
FILE rw-rw-r-- 21815 Jan 23 14:26 C64View.lha
FILE rw-rw-r-- 120 Jan 23 14:26 C64View.readme
Location: /mirrors/cpm
DIRECTORY rwxr-xr-x 512 c64
DIRECTORY rwxr-xr-x 1536 Nov 22 1992 c128
Host watsun.cc.columbia.edu (128.59.39.2)
Last updated 02:07 8 Sep 1993
Location: /kermit2/old
DIRECTORY rwxrwxr-x 1024 Jul 12 18:30 c64
Location: /kermit/bin
Host cs.columbia.edu (128.59.1.2)
Last updated 01:29 12 Sep 1993
Location: /archives/mirror1/kermit
FILE rw-rw-r-- 15016 Aug 24 1988 c644th.prg.gz
FILE rw-rw-r-- 733 Sep 29 1992 c64help.txt.gz
FILE rw-rw-r-- 6095 Sep 29 1992 c64ker1660.sda.gz
FILE rw-rw-r-- 5904 Sep 29 1992 c64kerfast.sda.gz
FILE rw-rw-r-- 26484 Sep 29 1992 c64kerv22a.sda.gz
FILE rw-rw-r-- 42552 Sep 29 1992 c64kerv22b.sda.gz
FILE rw-rw-r-- 31982 Sep 29 1992 c64slkv22s.sda.gz
Host plaza.aarnet.edu.au (139.130.4.6)
Last updated 00:00 28 Dec 1993
Location: /pub/kermit/c
FILE r--r--r-- 3073 Aug 16 1988 c64boot.bas
FILE r--r--r-- 1547 Aug 16 1988 c64boot.c
FILE r--r--r-- 1151 Aug 16 1988 c64boot.clu
FILE r--r--r-- 3002 Aug 16 1988 c64boot.for
FILE r--r--r-- 3315 Aug 16 1988 c64boot.sim
>There are more Kermit files which are not listed. Be sure to
>get the complete set of C64/128 Kermit files.
Host flubber.cs.umd.edu (128.8.128.99)
Last updated 00:00 03 Jan 1994
Location: /rec/newballistic
FILE rw-r--r-- 8576 Mar 23 21:21 balistic.c64
--------------------------------
Host f.ms.uky.edu (128.163.128.6)
Last updated 00:00 28 Dec 1993
Location: /archive/c64.zip
Host ftp.funet.fi (128.214.6.100)
Last updated 06:11 22 Mar 1993
Location: /pub/pics/jpeg/games
DIRECTORY rwxrwxr-x 512 Mar 20 02:07 c64
Location: /pub/misc
DIRECTORY rwxrwxr-x 512 Mar 13 23:30 c64
Location: /pub/kermit
DIRECTORY rwxrwxr-x 1024 Jan 13 1992 c64
Location: /pub/amiga/audio/misc/sid-tunes
FILE rw-rw-r-- 671490 Jun 18 1992 C64MusicShow-1.lha
FILE rw-rw-r-- 316521 Jun 18 1992 C64MusicShow-2.lha
/pub/cbm
Host nic.switch.ch (130.59.1.40)
Last updated 00:39 31 Aug 1993
Location: /mirror/kermit/bin
Host gmdzi.gmd.de (129.26.8.90)
Last updated 01:08 1 Aug 1993
Location: /if-archive/infocom/tools
FILE rw-rw-r-- 5668 Apr 27 15:00 c64.to.dat
Host micros.hensa.ac.uk (148.88.8.84)
Location /kermit
DIRECTORY rwxr-x--- 1024 Nov 11 09:20 c64
Host wilbur.stanford.edu (36.14.0.36)
Location /pub/emulators
DIRECTORY rwxr-xr-x 512 Jun 30 00:57 c64
Host syrinx.umd.edu (128.8.2.114)
Last updated 00:00 28 Dec 1993
Location: /rush/c64-sounds
Host tolsun.oulu.fi (130.231.96.16)
Last updated 01:53 6 Sep 1993
Location: /pub
DIRECTORY rwxr-xr-x 1024 Jul 15 1990 c64
Location: /incoming
DIRECTORY --------- 1024 Jun 20 1992 c64
/pub/amiga/4/c64trans.zoo
/pub/c64
>Uploading to /pub/c64 is disabled because of lack of disk space.
>However, for downloading it is still fully accessible.
>Currently there is no administration for /pub/c64.
>/pub/amiga is active, though.
Host ccosun.caltech.edu (131.215.139.2)
Last updated 00:00 31 JAN 1994
Location: /pub/rknop
Location: /pub/rknop/misc
> 64/128 programs can be found within directories according to
> function. When searching, be sure to check related directories.
Host ucsd.edu (128.54.16.1)
Last updated 04:46 6 Sep 1993
Location: /midi/software
DIRECTORY rwxr-xr-x 512 Jan 27 1992 c64
Host cs.dal.ca (129.173.4.5)
Last updated 01:36 12 Sep 1993
Location: /comp.archives
DIRECTORY rwxrwxr-x 3584 Apr 7 04:05 c64
pub/comp.archives/comp.sys.cbm
Host ccnga.uwaterloo.ca
Last updated 00:00 01 Jan 1994
Location: /pub/cbm/vbm110.uua
> For VBM Bitmap Viewer version 1.10
Host bert.psyc.upei.ca
Last updated 00:00 31 Jan 1994
Location: /pub
> All the releases of the major demo parties of '93
--------------------------------
Send all info regarding changes/additions/corrections [to the FTP list] to:
72560.3467@CompuServe.COM or: h.herman1@GEnie.geis.COM
=============================================================================
Hiding kilobytes
by Marko M"akel"a <Marko.Makela@Helsinki.FI>
Most Commodore 64 programs do not utilize even nearly all of the 64 kB
random access memory space. By default, there are only 44 kilobytes of
accessible RAM. This article describes how you can take the hiding 20
kilobytes to use.
_Memory management_
The Commodore 64 has access to more memory than its processor can
directly handle. This is possible by banking the memory. There are
five user configurable inputs that affect the banking. Three of them
can be controlled by program, and the rest two serve as control lines
on the memory expansion port.
The 6510 MPU has an integrated I/O port with six I/O lines. This
port is accessed through the memory locations 0 and 1. The location 0
is the Data Direction Register for the Peripheral data Register, which
is mapped to the other location. When a bit in the DDR is set, the
corresponding PR bit controls the state of a corresponding Peripheral
line as an output. When it is clear, the state of the Peripheral line
is reflected by the Peripheral register. The Peripheral lines are
numbered from 0 to 5, and they are mapped to the DDR and PR bits 0 - 5,
respectively. The 8502 processor, which is used in the Commodore 128,
has seven Peripheral lines in its I/O port. The seventh line is connected
to the Caps lock or ASC/CC key.
The I/O lines have the following functions:
Direction Line Function
--------- ---- --------
out P5 Cassette motor control. (0 = motor spins)
in P4 Cassette sense. (0 = PLAY button depressed)
out P3 Cassette write data.
out P2 CHAREN
out P1 HIRAM
out P0 LORAM
The default value of the DDR register is $2F, so all lines except
Cassette sense are outputs. The default PR value is $37 (Datassette
motor stopped, and all three memory management lines high).
Like most chips in the Commodore 64, the 6510 MPU uses the NMOS
(N-channel metal oxide semiconductor) technology. The NMOS switches
produce strong logical '0' levels, but weak '1' levels. The opposite
is the PMOS (P-channel metal oxide semiconductor) technology, which
cannot pull strong signals low, but is able to drive them high. The CMOS
technology (complementary metal oxide semiconductor), which combines
these two technologies, is able to drive both logical levels.
Because most integrated circuits in the C64 use the NMOS technology,
all hardware lines that are not outputs are driven to +5 volts with a
weak current. This is usually accomplished by pull-up resistors, large
resistances between the hardware lines and the +5 volt power supply
line. The resistors can be inside a chip or on the printed circuit
board. This allows any NMOS or CMOS chip to drive the line to the
desired state (low or high voltage level).
The difference between an input and an output is that an output uses
more current to drive the signal to the desired level. An input and an
output outputting logical '1' are equivalent for any other inputting
chip. But if a chip is trying to drive a signal to ground level, it
needs more current to sink an output than an input. You can even use
outputs as inputs, i.e. read them in your program.
You can use this feature to distinquish between the left
shift and the shift lock keys, although they are connected
to same hardware lines. The shift lock key has smaller
resistance than the left shift. If you make both CIA 1
ports to outputs (write $FF to $DC03 and $DC01) prior
reading the left shift key, only shift lock can change the
values you read from CIA 1 port B ($DC01).)
So, if you turn any memory management line to input, the external
pull-up resistors will make it look like it is outputting logical
'1'. This is actually why the computer always switches the ROMs in
upon startup: Pulling the -RESET line low resets all Peripheral lines
to inputs, thus driving all three processor-driven memory management
lines high.
The two remaining memory management lines are -EXROM and -GAME on
the cartridge port. Each line has a pull-up resistor, so the lines are
'1' by default. (In the Commodore 128, you can set the state of these
two lines prior to selecting the C64 mode, provided that you write the
mode switch routine yourself.)
Even though the memory banking has been implemented with a 82S100
Programmable _Logic_ Array, there is only one control line that seems
to behave logically at first sight, the -CHAREN line. It is mostly
used to choose between I/O address space and the character generator
ROM. The following memory map introduces the oddities of -CHAREN and
the other memory management lines. It is based on the memory maps in
the Commodore 64 Programmer's Reference Guide, pp. 263 - 267, and some
errors and inaccuracies have been corrected.
The leftmost column of the table contains addresses in hexadecimal
notation. The columns aside it introduce all possible memory
configurations. The default mode is on the left, and the absolutely
most rarely used Ultimax game console configuration is on the right.
(There have been at least two Ultimax cartridges on the market.) Each
memory configuration column has one or more four-digit binary numbers
as a title. The bits, from left to right, represent the state of the
-LORAM, -HIRAM, -GAME and -EXROM lines, respectively. The bits whose
state does not matter are marked with "x". For instance, when the
Ultimax video game configuration is active (the -GAME line is shorted
to ground, -EXROM kept high), the -LORAM and -HIRAM lines have no effect.
default Ultimax
1111 101x 1000 011x 001x 1110 0100 1100 xx01
00x0
10000
-----------------------------------------------------------------------------
F000
Kernal RAM RAM Kernal RAM Kernal Kernal Kernal ROMH(*
E000
-----------------------------------------------------------------------------
D000 IO/C IO/C IO/RAM IO/C RAM IO/C IO/C IO/C I/O
-----------------------------------------------------------------------------
C000 RAM RAM RAM RAM RAM RAM RAM RAM -
-----------------------------------------------------------------------------
B000
BASIC RAM RAM RAM RAM BASIC ROMH ROMH -
A000
-----------------------------------------------------------------------------
9000
RAM RAM RAM RAM RAM ROML RAM ROML ROML(*
8000
-----------------------------------------------------------------------------
7000
6000
RAM RAM RAM RAM RAM RAM RAM RAM -
5000
4000
-----------------------------------------------------------------------------
3000
2000 RAM RAM RAM RAM RAM RAM RAM RAM -
1000
-----------------------------------------------------------------------------
0000 RAM RAM RAM RAM RAM RAM RAM RAM RAM
-----------------------------------------------------------------------------
*) Internal memory does not respond to write accesses to these areas.
Legend: Kernal E000-FFFF Kernal ROM.
IO/C D000-DFFF I/O address space or Character
generator ROM, selected by -CHAREN.
If the CHAREN bit is clear,
the character generator ROM is
chosen. If it is set, the
I/O chips are accessible.
IO/RAM D000-DFFF I/O address space or RAM,
selected by -CHAREN.
If the CHAREN bit is clear,
the character generator ROM is
chosen. If it is set, the
internal RAM is accessible.
I/O D000-DFFF I/O address space.
The -CHAREN line has no effect.
BASIC A000-BFFF BASIC ROM.
ROMH A000-BFFF or External ROM with the -ROMH line
E000-FFFF connected to its -CS line.
ROML 8000-9FFF External ROM with the -ROML line
connected to its -CS line.
RAM various ranges Commodore 64's internal RAM.
- 1000-7FFF and Open address space.
A000-CFFF The Commodore 64's memory chips
do not detect any memory accesses
to this area except the VIC-II's
DMA and memory refreshes.
NOTE: Whenever the processor tries to write to any ROM area
(Kernal, BASIC, CHAROM, ROML, ROMH), the data will get
"through the ROM" to the C64's internal RAM.
For this reason, you can easily copy data from ROM to RAM,
without any bank switching. But implementing external
memory expansions without DMA is very hard, as you have to
use the Ultimax memory configuration, or the data will be
written both to internal and external RAM.
However, this is not true for the Ultimax game
configuration. In that mode, the internal RAM ignores all
memory accesses outside the area $0000-$0FFF, unless they are
performed by the VIC, and you can write to external memory
at $1000-$CFFF and $E000-$FFFF, if any, without changing
the contents of the internal RAM.
_A note concerning the I/O area_
The I/O area is divided as follows:
Address range Owner
------------- -----
D000-D3FF MOS 6567/6569 VIC-II Video Interface Controller
D400-D7FF MOS 6581 SID Sound Interface Device
D800-DBFF Color RAM (only lower nybbles are connected)
DC00-DCFF MOS 6526 CIA Complex Interface Adapter #1
DD00-DDFF MOS 6526 CIA Complex Interface Adapter #2
DE00-DEFF User expansion #1 (-I/O1 on Expansion Port)
DF00-DFFF User expansion #2 (-I/O2 on Expansion Port)
As you can see, the address ranges for the chips are much larger
than required. Because of this, you can access the chips through
multiple memory areas. The VIC-II appears in its window every $40
addresses. For instance, the addresses $D040 and $D080 are both mapped
to the Sprite 0 X co-ordinate register. The SID has one register
selection line less, thus it appears at every $20 bytes. The CIA
chips have only 16 registers, so there are 16 copies of each in their
memory area.
However, you should not use other addresses than those specified by
Commodore. For instance, the Commodore 128 mapped its additional I/O
chips to this same memory area, and the SID responds only to the
addresses D400-D4FF, also when in C64 mode. And the Commodore 65,
which unfortunately did not make its way to the market, could narrow
the memory window reserved for the MOS 6569/6567 VIC-II (or CSG 4567
VIC-III in that machine).
_The video chip_
The MOS 6567/6569 VIC-II Video Interface Controller has access to
only 16 kilobytes at a time. To enable the VIC-II to access the whole
64 kB memory space, the main memory is divided to four banks of 16 kB
each. The lines PA0 and PA1 of the second CIA are the inverse of the
virtual VIC-II address lines VA14 and VA15, respectively. To select a
VIC-II bank other than the default, you must program the CIA lines to
output the desired bit pair. For instance, the following code selects
the memory area $4000-$7FFF (bank 1) for the video controller:
LDA $DD02 ; Data Direction Register A
ORA #$03 ; Set pins PA0 and PA1 to outputs
STA $DD02
LDA $DD00
AND #$FC ; Mask the lowmost bit pair off
ORA #$02 ; Select VIC-II bank 1 (the inverse of binary 01 is 10)
STA $DD00
Why should you set the pins to outputs? Hardware RESET resets all
I/O lines to inputs, and thanks to the CIA's internal pull-up
resistors, the inputs actually output logical high voltage level. So,
upon -RESET, the video bank 0 is selected automatically, and older
Kernals could leave it uninitialized.
Note that the VIC-II always fetches its information from the
internal RAM, totally ignoring the memory configuration lines. There
is only one exception to this rule: The character generator ROM.
Unless the Ultimax mode is selected, VIC-II "sees" character generator
ROM in the memory areas 1000-1FFF and 9000-9FFF. If the Ultimax
configuration is active, the VIC-II will fetch all data from the
internal RAM.
_An application: Making an operating system extension_
If you are making a memory resident program and want to make it as
invisible to the system as possible, probably the best method is
keeping most of your code under the I/O area (in the RAM at
$D000-$DFFF). This area is very safe, since programs utilizing it are
rare, since they are very difficult to implement and to debug. You
need only a short routine in the normally visible RAM that pushes the
current value of the processor's I/O register $01 on stack, switches
RAM on to $D000-$DFFF and jumps to this area. Returning from the
$D000-$DFFF area is possible even without any routine in the normally
visible RAM area. Just write an RTS or an RTI to an I/O register and
return through it.
But what if your program needs to use I/O? And how can you write the
return instruction to an I/O register while the I/O area is switched
off? You need a swap area for your program in normally visible memory.
The first thing your routine at $D000-$DFFF does is copying the I/O
routines (or the whole program) to normally visible memory, swapping
the bytes. For instance, if your I/O routines are initially being
stored at $D200-$D3FF, exchange the bytes in $D200-$D3FF with the
contents of $C000-$C1FF. Now you can call the I/O routines from your
routine at $D000-$DFFF, and the I/O routines can switch the I/O area
temporarily on to access the I/O chips. And right before exiting your
program at $D000-$DFFF swaps the old contents of that I/O routine area
in, e.g. exchanges the memory areas $D200-$D3FF and $C000-$C1FF
again.
What I/O registers can you use for the return instruction? There are
basically two alternatives: 8-bit VIC sprite registers or either CIA's
serial port register. The VIC registers are easiest to use, as they
act precisely like memory places: you can easily write the desired
value to a register. But the CIA register is usually better, as
changing the VIC registers might change the screen layout.
However, also the SP register has some drawbacks: If the machine's
CNT1 and CNT2 lines are connected to a frequency source, you must stop
either CIA's Timer A to use the SP register method. Normally the 1st
CIA's Timer A is the main hardware interrupt source. And if you use
the Kernal's RS232, you cannot stop the 2nd CIA's Timer A either. Also,
if you don't want to lose any CIA interrupts, you might want to know
that executing the RTS or RTI at SP register has the side effect of
reading the Interrupt Control Register, thus acknowledging an interrupt
that might have been waiting.
If you can't use either method, you can use either CIA's ToD seconds
or minutes or ToD alarm time for storing an RTI. Or, if you don't want
to alter any registers, use the VIC-II's light pen register. Before
exiting, wait for appropriate raster line and trig the light pen latch
with CIA1's PB4 bit. However, this method assumes that the control
port 1's button/light pen line remains up for that frame. After
trigging the light pen, causing the light pen Y co-ordinate register
($D014) to be $40 or $60, you have more than half a frame time to
restore the state of the I/O chips and return through the register.
You can also use the SID to store an RTI or RTS command. How is this
possible, you might ask. After all, the chip consists of read only or
write only registers. However, there are two registers that can be
controlled by program, the envelope generator and oscillator outputs
of the third voice. This method requires you to change the frequency
of voice 3 and to select a waveform for it. This will affect on the
voice output by turning the voice 3 off, but who would keep the voice
3 producing a tone while calling an operating system routine?
Also keep in mind that the user could press RESTORE while the Kernal
ROM and I/O areas are disabled. You could write your own non-maskable
interrupt (NMI) handler (using the NMI vector at $FFFA), but a fast
loader that uses very tight timing would still stop working if the
user pressed RESTORE in the middle of a data block transfer. So, to
make a robust program, you have to disable NMI interrupts. But how is
this possible? They are Non-Maskable after all. The NMI interrupt is
edge-sensitive, the processor jumps to NMI handler only when the -NMI
line drops from +5V to ground. To disable the interrupt, simply cause
an NMI with CIA2's timer, but don't read the Interrupt Control
register. If you need to read $DD0D in your program, you must add a
NMI handler just in case the user presses RESTORE. And don't forget to
raise the -NMI line upon exiting the program. Otherwise the RESTORE
key does not work until the user issues a -RESET or reads the ICR
register explicitly. (The Kernal does not read $DD0D, unless it is
handling an interrupt.) This can be done automatically by the two
following SP register examples due to one of the 6510's undocumented
features (refer to the descriptions of RTS and RTI below).
; Returning via VIC sprite 7 X co-ordinate register
Initialization: ; This is executed when I/O is switched on
LDA #$60
STA $D015 ; Write RTS to VIC register $15.
Exiting: ; NOTE: This procedure must start at VIC register
; $12. You have multiple alternatives, as the VIC
; appears in memory at $D000+$40*n, where $0<=n<=$F.
PLA ; Pull the saved 6510 I/O register state from stack
STA $01 ; Restore original memory bank configuration
; Now the processor fetches the RTS command from the
; VIC register $15.
; Returning via CIA 2's ToD or ToD alarm seconds register
Initialization: ; This is executed when I/O is switched on
LDA #$40
STA $DD08 ; Set ToD tenths of seconds
; (clear it so that the seconds register
; would not overflow)
; If ToD alarm register is selected, this
; instruction will be unnecessary.
STA $DD09 ; Set ToD seconds
LDA $DD0B ; Read ToD hours (freeze ToD display)
Exiting: ; NOTE: This procedure must start at CIA 2 register
; $6. As the CIA 2 appears in memory at $DD00+$10*n,
; where 0<=n<=$F, you have sixteen alternatives.
PLA
STA $01 ; Restore original memory bank configuration
; Now the processor fetches the RTS command from
; the CIA 2 register $9.
; Returning via CIA 2's SP register (assuming that CNT2 is stable)
Initialization: ; This is executed when I/O is switched on
LDA $DD0E ; CIA 2's Control Register A
AND #$BF ; Set Serial Port to input
STA $DD0E ; (make the SP register to act as a memory place)
LDA #$60
STA $DD0C ; Write RTS to CIA 2 register $C.
Exiting: ; NOTE: This procedure must start at CIA 2 register
; $9. As the CIA 2 appears in memory at $DD00+$10*n,
; where 0<=n<=$F, you have sixteen alternatives.
PLA
STA $01 ; Restore original memory bank configuration
; Now the processor fetches the RTS command from
; the CIA 2 register $C.
; Returning via CIA 2's SP register, stopping the Timer A
; and forcing SP2 and CNT2 to output
Initialization: ; This is executed when I/O is switched on
LDA $DD0E ; CIA 2's Control Register A
AND #$FE ; Stop Timer A
ORA #$40 ; Set Serial Port to output
STA $DD0E ; (make the SP register to act as a memory place)
LDA #$60
STA $DD0C ; Write RTS to CIA register $C.
Exiting: ; NOTE: This procedure must start at CIA 2 register
; $9. As the CIA 2 appears in memory at $DD00+$10*n,
; where 0<=n<=$F, you have sixteen alternatives.
PLA
STA $01 ; Restore original memory bank configuration
; Now the processor fetches the RTS command from
; the CIA 2 register $C.
; Returning via SID oscillator 3 output register
Initialization: ; This is executed when I/O is switched on
LDA #$20 ; Select sawtooth waveform
STA $D412 ; but do not enable the sound
LDY #$00 ; Select frequency
STY $D40E ; (system clock)/$FF00,
LDA #$FF ; causing the OSC3 output to increment by one
STY $D40F ; every $10000/$FF00 cycles.
LDA #$0E
LDX #$60
BIT $D41B ; Wait for the oscillator 3 output
BMI *-3 ; to be in the range
BVS *-5 ; $00-$3F.
BIT $D41B ; Wait for the oscillator 3 output
BVC *-3 ; to be at least $40.
STA $D40F ; Slow down the frequency to (system clock)/$0E00.
CPX $D41B ; Wait for the oscillator 3
BNE *-3 ; output to reach $60 (RTS)
STY $D40F ; Reset the frequency of voice 3
; (stop the OSC3 register from increasing)
Exiting: ; NOTE: This procedure must start at SID register
; $18. As the SID appears in memory at $D400+$20*n,
; where 0<=n<=$20, you have thirty-two alternatives.
; However, in C128 there are only eight alternatives,
; as the SID is only at $D400-$D4FF.
PLA
STA $01 ; Restore original memory bank configuration
; Now the processor fetches the RTS command from
; the SID register $1B.
For instance, if you want to make a highly compatible fast loader,
make the ILOAD vector ($0330) point to the beginning of the stack
area. Remember that the BASIC interpreter uses the first bytes of
stack while converting numbers to text. A good address is $0120.
Robust programs practically never use so much stack that it could
corrupt this routine. Usually only crunched programs (demos and alike)
use all stack in the decompression phase. They also make use of the
$D000-$DFFF area.
This stack routine will jump to your routine at $D000-$DFFF, as
described above. For performance's sake, copy the whole byte transfer
loop to the swap area, e.g. $C000-$C1FF, and call that subroutine
after doing the preliminary work. But what about files that load over
$C000-$C1FF? Wouldn't that destroy the transfer loop and jam the
machine? Not necessarily. If you copy those bytes to your swap area at
$D000-$DFFF, they will be loaded properly, as your program restores
the original $C000-$C1FF area.
If you want to make your program user-friendly, put a vector
initialization routine to the stack area as well, so that the user can
restore the fast loader by issuing a SYS command, rather than loading
it each time he has pressed RESET.
_An example: A "hello world" program_
To help you in getting started, I have written a small example
program that echoes the famous message "hello, world!" to standard
output (normally screen) using the Kernal's CHROUT subroutine. After
the initialization routine has been run, the program can be started by
commanding SYS 300. I used the Commodore 128's machine language
monitor to put it up, but it was still pretty difficult to debug the
program. Here it is in uuencoded format:
begin 644 hello
M`0@+",D'GC(P-C
gemini - kennedy.gemi.dev
``!XI0%(*?B%`:(,O3`(G2P!RA#WHHN]/`B=8]W*T/=H
MA0%88*4!JBGX"01XA0%,I-WF`:*!C@W=H@".!=WHC@3=HMV.#MVB0(X,W<8!
M8*4!2`D#A0&@#+DSP"#2_X@0]VB%`6`A1$Q23U<@+$],3$5(BDBM^O](K?O_
M2*D6C?K_J<"-^_\@W-T@`,!HC?O_:(WZ_R`=P"#<W6BHJ0!(NOX"`=`#_@,!
5A`&@/[X`P+EDW9D`P(J99-V($/!@
`
end
In order to fully understand the operation of this program, you need
to know how the instructions RTI, RTS and PHA work. There is some work
going on to reverse engineer the NMOS 6502 microprocessor to large
extent, and it is now known for most instructions what memory places
they access during their execution and for what purpose. The internal
procedures haven't been described in detail yet, but these
descriptions should be easier to read anyway.
For curiosity, I quote here the description of all instructions that
use the stack. The descriptions of internal operations are yet
inaccurate, but the memory accesses have been verified with an
oscilloscope. I will mail copies the whole document upon request. When
finished, the document will be put on an FTP site.
JSR
# address R/W description
--- ------- --- -------------------------------------------------
1 PC R fetch opcode, increment PC
2 PC R fetch address's low byte to latch, increment PC
3 $0100,S R
4 $0100,S W push PCH on stack, decrement S
5 $0100,S W push PCL on stack, decrement S
6 PC R copy latch to PCL, fetch address's high byte to
latch, copy latch to PCH
RTS
# address R/W description
--- ------- --- -----------------------------------------------
1 PC R fetch opcode, increment PC
2 PC R read next instruction byte (and throw it away),
increment PC
3 $0100,S R increment S
4 $0100,S R pull PCL from stack, increment S
5 $0100,S R pull PCH from stack
6 PC R increment PC
BRK
# address R/W description
--- ------- --- -----------------------------------------------
1 PC R fetch opcode, increment PC
2 PC R read next instruction byte (and throw it away),
increment PC
3 $0100,S W push PCH on stack, decrement S
4 $0100,S W push PCL on stack, decrement S
5 $0100,S W push P on stack (with B flag set), decrement S,
set I flag
6 $FFFE R fetch PCL
7 $FFFF R fetch PCH
RTI
# address R/W description
--- ------- --- -----------------------------------------------
1 PC R fetch opcode, increment PC
2 PC R read next instruction byte (and throw it away),
increment PC
3 $0100,S R increment S
4 $0100,S R pull P from stack, increment S
5 $0100,S R pull PCL from stack, increment S
6 $0100,S R pull PCH from stack
PHA, PHP
# address R/W description
--- ------- --- -----------------------------------------------
1 PC R fetch opcode, increment PC
2 PC R read next instruction byte (and throw it away),
increment PC
3 $0100,S W push register on stack, decrement S
PLA, PLP
# address R/W description
--- ------- --- -----------------------------------------------
1 PC R fetch opcode, increment PC
2 PC R read next instruction byte (and throw it away),
increment PC
3 $0100,S R increment S
4 $0100,S R pull register from stack
The example program consists of three parts. The first part
transfers the other parts to appropriate memory areas. The second part
is located in stack area (300-312), and it invokes the third part, the
main module.
The loader part ($0801-$08C7) is as follows:
1993 SYS2061
080D SEI Disable interrupts.
080E LDA $01
0810 PHA Store the state of the processor's I/O lines.
0811 AND #$F8
0813 STA $01 Select 64 kB RAM memory configuration.
0815 LDX #$0C Copy the invoking part to 300-312.
0817 LDA $0830,X
081A STA $012C,X
081D DEX
081E BPL $0817
0820 LDX #$8B Copy the main part to $DD64-$DDEE.
0822 LDA $083C,X
0825 STA $DD63,X
0828 DEX
0829 BNE $0822
082B PLA Restore original memory configuration.
082C STA $01
082E CLI Enable interrupts.
082F RTS Return.
The user invokes the following part by issuing SYS 300. This part
changes the memory configuration and jumps to the main part.
012C LDA $01
012E TAX Store original memory configuration to X register.
012F AND #$F8
0131 ORA #$04
0133 SEI Disable interrupts.
0134 STA $01 Select 64 kB RAM memory configuration.
0136 JMP $DDA4 Jump to the main part.
The main part actually consists of two parts. It may be a bit
complicated, and it might teach new tricks to you.
DDA4 TXA
DDA5 PHA Push original memory configuration on stack.
DDA6 LDA $FFFA
DDA9 PHA
DDAA LDA $FFFB
DDAD PHA Store the original values of $FFFA and $FFFB.
DDAE LDA #$16
DDB0 STA $FFFA Set ($FFFA) to point to RTI.
DDB3 LDA #$C0
DDB5 STA $FFFB
DDB8 JSR $DDDC Swap the auxiliary routines in.
DDBB JSR $C000 Disable NMI's and initialize CIA2.
DDBE PLA
DDBF STA $FFFB Restore original values to $FFFA and $FFFB.
DDC2 PLA
DDC3 STA $FFFA
DDC6 JSR $C01D Print the message.
DDC9 JSR $DDDC Swap the auxiliary routines out.
DDCC PLA
DDCD TAY Load original memory configuration to Y register.
DDCE LDA #$00 Push desired stack register value on stack
DDD0 PHA (clear all flags, especially the I flag).
DDD1 TSX
DDD2 INC $0102,X Increment the return address.
DDD5 BNE $DDDA (RTS preincrements it, but RTI does not.)
DDD7 INC $0103,X
DDDA STY $01 Restore original memory configuration.
(The 6510 fetches the next instruction from $DDDC, which is now
connected to the CIA2's register $C, the Serial Port register.
The initialization routine wrote an RTI to it. The processor also
reads from $DDDD as a side effect of the instruction fetch,
thus re-enabling NMI's.)
DDDC LDY #$3F Subroutine: Swap the memory areas $C000-$C03F
DDDE LDX $C000,Y and $DD64-$DDA3 with each other.
DDE1 LDA $DD64,Y
DDE4 STA $C000,Y
DDE7 TXA
DDE8 STA $DD64,Y
DDEB DEY
DDEC BPL $DDDE
DDEE RTS
C000 INC $01 Enable the I/O area.
C002 LDX #$81
C004 STX $DD0D Enable Timer A interrupts of CIA2.
C007 LDX #$00
C009 STX $DD05
C00C INX
C00D STX $DD04 Prepare Timer A to count from 1 to 0.
C010 LDX #$DD
C012 STX $DD0E Cause an interrupt.
(The instruction sets SP to output, makes Timer A to count
system clock pulses, forces the CIA to load the initial value
to the counter, selects one-shot counting and starts the timer.)
C015 LDX #$40
(The processor now jumps to the NMI handler ($C016), and
the SP register starts to act as a memory place.)
C017 STX $DD0C Write an RTI to Serial Port register.
C01A DEC $01 Disable the I/O area.
C01C RTS Return.
C01D LDA $01
C01F PHA
C020 ORA #$03 Enable I/O and ROMs.
C022 STA $01
C024 LDY #$0C Print the message.
C026 LDA $C033,Y
C029 JSR $FFD2
C02C DEY
C02D BPL $C026
C02F PLA
C030 STA $01 Restore the 64 kB memory configuration.
C032 RTS
C033 "!DLROW ,OLLEH"
(The string is backwards in memory, since I don't want to
waste cycles in explicit comparisons. This method results in
more readable code than doing a forward loop with an index
value $100-(number of characters).)
This program is not excellent. It has the following bugs:
o The 6510's memory management lines P0 and P1 (LORAM and HIRAM,
respectively) are assumed to be outputs. If you issued the
command POKE0,PEEK(0)AND252, this program would not work.
This could be easily corrected by setting the P0 and P1 lines
to output in the beginning of the interfacing routine (300 - 312):
LDA $00
ORA #$02
STA $00
o The program does not restore the original state of the CIA2
Control Register A or Interrupt Control Register. It might be
impossible to start using the Kernal's RS-232 routines after
running this.
o If the user redirected output to cassette or RS-232, interrupts
would be required. However, they are completely disabled.
o If a non-maskable interrupt occurs while the loader part is being
executed, the program will screw up. This will happen also in the
main part, if an NMI is issued after disabling ROMs and I/O in
$0134 but before exchanging the contents of the memory places
$C016 and $DD7A.
_Freezer cartridges_
There are many cartridges that let you to stop almost any program for
"back-up" purposes. One of the most popular of these freezer
cartridges is the Action Replay VI made by Datel Electronics back in
1989. The cartridge has 8 kilobytes RAM and 32 kilobytes ROM on board,
and it has a custom chip for fiddling with the C64 cartridge port
lines -EXROM, -GAME, -IRQ, -NMI and BA.
If the -NMI line is not asserted (the NMI interrupts are enabled), all
freezer cartridges should be able to halt any program. When the user
presses the "freeze" button, the cartridges halt the processor by
dropping the BA line low. Then they switch some of their own ROM to
the $E000 - $FFFF block by selecting the UltiMax configuration with
the -EXROM and -GAME lines. After this, they assert the -NMI line and
release the BA line. After completing the current instruction, the
processor will take the NMI interrupt and load the program counter
from the vector at $FFFA, provided that the NMI line was not asserted
already.
This approach is prone to many flaws. Firstly, if the processor is
executing a write instruction when the program is being halted, and if
the write occurred outside the area $0000 - $0FFF, the data would get
lost, if the UltiMax configuration was asserted too early. This can be
corrected to some extent by waiting at least two cycles after
asserting the BA line, as the processor will not stop during write
cycles. However, this is of no help if the processor has not gotten to
the write stage yet.
Secondly, if the instruction being executed is outside the area
$0000 - $0FFF, or if it accesses any data outside that area, the
processor will fetch either wrong parameters or incorrect data, or
both. If the instruction does not write anything, will only corrupt
one processor register.
Thirdly, if the NMI interrupts are disabled, pressing the "freeze"
button does not have any other immediate effect than leaving the
UltiMax mode asserted, which makes any system RAM outside the area
$0000 - $0FFF unavailable. It also forces the I/O area ($D000 - $DFFF)
on. If the program has any instructions or data outside the lowmost
four kilobytes, it will eventually jam, as that data will be something
else than the program expects.
One might except that reading from open address space should return
random bytes. But, in at least two C64's, the bytes read are mostly
$BD, which is the opcode for LDA absolute,X. So, if the processor has
a "good luck", it will happily execute only LDA $BDBD,X commands, and
it might survive to the cartridge ROM area without jamming. Or it
could eventually fetch a BRK and jump to the cartridge ROM via the
IRQ/BRK vector at $FFFE. The Action Replay VI has the familiar
autostart data in the beginning of both the ROML and ROMH blocks by
default, and that data could be interpreted as sensible commands. The
Action Replay VI was indeed able to freeze my test program, even
though I had covered its -RESET, -IRQ and -NMI lines with a piece of
tape, until I relocated the program to the first 4 kilobyte block.
_Building an unbeatable freezer circuit_
As you can see, it is totally impossible to design a freezer cartridge
that freezes any program. If the program to be freezed has disabled
the NMI interrupts, and if its code runs mostly at $0000 - $0FFF or
$D000 - $DFFF, the computer will more probably hang than succeed in
freezing the program.
However, it is possible to make some internal modifications to a C64,
so that it can freeze literally any program. You need to expand your
machine to 256 kilobytes following the documents on ftp.funet.fi in
the /pub/cbm/hardware/256kB directory. It will let you to reset the
computer so that all of the 64 kilobytes the previous program used,
will remain intact. If you add a switch to one of the memory expansion
controller's chip selection lines, the program being examined will
have no way to screw the machine up, as the additional memory management
registers will not be available.
A few enhancements to this circuit are required so that you can freeze
the programs without losing the state of the I/O chips. You will also
need to replace the Kernal ROM chip with your own code, if you do not
want to lose the state of the A, X, P and S registers. Unfortunately
this circuit will not preserve the state of the processor's Peripheral
lines (its built-in I/O port mapped to the memory addresses 0 and 1),
nor does it record the program counter (PC). I have a partial solution
to the PC problem, though.
If you are interested in this project, contact me. I will design the
additional hardware, and I will program the startup routines, but I
certainly do not have the time to program all of the freezer software.
Most of the freezer software could be in RAM, so it would be very easy
to develop it, and you could even use existing tools by patching them
slightly.
=============================================================================
FLD - Scrolling the screen
by Marek Klampar (klampar@elf.stuba.sk)
Scrolling the screen
--------------------
[inspirated by Pasi Ojala article 'Opening the borders' from issue#6]
From Pasi 'Albert' Ojala's (po87553@cs.tut.fi or albert@cc.tut.fi) article:
_Scrolling the screen_
VIC begins to draw the screen from the first bad line. VIC will know
what line is a bad line by comparing its scan line counter to the
vertical scroll register : when they match, the next line is a bad
line. If we change the vertical scroll register ($d011), the first bad
line will move also. If we do this on every line, the line counter in
VIC will never match with it and the drawing never starts (until it is
allowed to do so).
When we don't have to worry about bad lines, we have enough time to
open the borders and do some other effects too. It is not necassary to
change the vertical scroll on every line to get rid of the bad lines,
just make sure that it never matches the line counter (or actually the
least significant 3 bits).
You can even scroll the bad lines independently and you have FLD -
Flexible Line Distance. You just allow a bad line when it is time to
display the next character row. With this you can bounce the lines or
scroll a hires picture very fast down the screen.
(*** end of Albert's paragraph ***)
Well, everything important was written. I'm just adding this:
For moving hires picture replace ORA #$10 by ORA #$30.
For another FX try to replace part of irq routine begining with ORA #$10 by:
ORA #$C0
STA $D016,
remove JSR CHOFS,
replace LDX OFSET
by LDX #$ff
and enjoy =)
The demonstartion program for FLD application
;---------------------------------------
; Commodore Cracker 1993
;---------------------------------------
FROM = $32
TO = $FA
;---------------------------------------
*= $C000
;---------------------------------------
INIT LDA #0
STA DIR ; Direction
LDA #$FF ; Set garbage
STA $3FFF
LDA #FROM
STA OFSET ; Set ofset
SEI ; Disable interrupt
LDA #$7F ; Disable timer interrupt
STA $DC0D
LDA #1 ; Enable raster interrupt
STA $D01A
LDA #<IRQ ; Set irq vector
STA $0314
LDA #>IRQ
STA $0315
LDA #0 ; To evoke our irq routine on 0th line
STA $D012
CLI ; Enable interrupt
RTS
;---------------------------------------
IRQ LDX OFSET
L2 LDY $D012 ; Moving 1st bad line
L1 CPY $D012
BEQ L1 ; Wait for begin of next line
DEY ; IY - bad line
TYA
AND #$07 ; Clear higher 5 bits
ORA #$10 ; Set text mode
STA $D011
DEX
BNE L2
INC $D019 ; Acknowledge the raster interrupt
JSR CHOFS
JMP $EA31 ; Do standard irq routine
;---------------------------------------
OFSET .BYTE FROM
DIR .BYTE 0
;---------------------------------------
CHOFS LDA DIR ; Change OFSET of screen
BNE UP
INC OFSET ; Down
LDA OFSET
CMP #TO
BNE SKIP
STA DIR
SKIP RTS
;---------------------------------------
UP DEC OFSET ; Up
LDA OFSET
CMP #FROM
BNE SKIP
LDA #0
STA DIR
RTS
=============================================================================
Tech-tech - more resolution to vertical shift.
by Pasi 'Albert' Ojala (po87553@cs.tut.fi _or_ albert@cc.tut.fi)
Written on 16-May-91 Translation 02-Jun-92
(All timings are in PAL, principles will apply to NTSC too)
One time half of the demos had pictures waving horizontally on the
width of the whole screen. This effect is named tech-tech, and the
audience was puzzled. You can move the screen only eight pixels using
the horizontal scroll register. This effect was done using character
graphics. How exactly and is the same possible with sprites ?
Horizontal scroll register can move the screen by eight pixels. This
isn't even nearly enough to produce a really stunning effect. You have
to move the graphics itself, fortunately with a resolution of one
character position (one byte) only, the rest can be done with the scroll
register. During one scan line there is no time to move the actual data,
you can only move a pointer. Changing the video matrix pointer won't
help, because VIC (video interface controller) will fetch the character
codes only at certain times, called bad lines. You can change the
character set pointer instead, because VIC reads the data it displays
directly from the character set memory.
Character set-implementation has its restrictions
Because horizontal movement is done by changing the character sets, the
picture or text must be pure graphic and the character codes in the
video matrix must be in a numerical order. The normal picture is in the
first character memory and in the next one it is shifted one character
position to the right. One video bank can hold only seven full character
memories besides the video matrix. This limits the movement of the
picture to 56 pixels. It is possible to get more movement if you use
smaller picture or another video bank.
The shift is done so that on each scan line we update the horizontal
scroll register ($D016) with the three lowest bits of the shift value.
We use the other bits to select the right character set ($D018). In a
tech-tech the shift value changes during the display of the whole
picture, and the values are stored in a table. In addition to that, the
shift values should be put into two tables, one for the horizontal
scroll register and another for the character set select. This is
necessary, because there is no time for extra calculations on a bad
line.
Because we have to change the character set and x-scroll dynamically, we
also need a raster routine to show a tech-tech. A raster routine is a
routine which is synchronized to the electron beam. This eats up the
processor time: the bigger the picture, the less time is left over for
other activities. On other than bad lines you can do other funny things,
like change the color of the background or border.
An example program
The demo program uses video bank 2, memory addesses $4000-7fff. The
video matrix is in the beginning of the bank. Only inverted chars are
used for the graphics, this way we have all eight character memories
available and the maximum shift is 64 pixels. The area for the tech-tech
in the video matrix is eight character rows high, but it has identical
graphics on every line. This is why we use only 320 bytes from each
character set.
You can use a joystick to control the movement of the tech-tech. The
stick decreases or increases the shift add value in a resolution of a
half pixel. When the shift reaches its highest/lowest value, the
direction of the add is reversed. Just experiment with it.
You can do it on the screen, how about borders ?
Because you cannot get characters to the border, you might think that it
is impossible to make a tech-tech effect in the borders. It takes so
much time to change sprite x-coordinates, that you can change only some
of them. There is time for five sprite moves, if you do not need to
change the most significant (9th) bit of the x-coordinate. On the other
hand, you could design the movements directly to the sprites and then
just change the images, but then the movements would be constant.
However, there is one trick you can use to get all of the sprites on the
screen, with variable movements and color bars etc. You do not change
the x-coordinates, but the data itself on each scan line. In fact you
change the sprite image pointers. There is multiple sprite pictures,
where the graphics is shifted horizontally, just like the normal
tech-tech charsets. Because of this, the sprites have to be placed side
by side. No gaps are allowed. By changing the image pointers you can get
the graphics to move horizontally on each line as you wish. With
multicolor sprites you have to remember that one pixel corresponds to
two bits - the movement is not so smooth.
Wait ! How come there is enough time to change the sprite pointers, when
there is not time to change the coordinates ? This is another pointer
trick. VIC reads the sprite image pointers from the end of the current
video matrix, normally $07f8. You just have to change the video matrix
pointer ($D018) to change all of the image pointers. This takes only
eight cycles and there is plenty of time left for other effects on each
scan line. If you use only one video bank, you can get the sprite
picture to 16 different places. This allows also another kind of
effects, just use your imagination.
--------------------------------------------------------------------------
Tech-tech demo program (PAL)
BANK= $96 ; The value of the video bank register (CIA2) in the tech-area
ZP= $FB ; Zero page for indirect addressing
START= $4400 ; Start of the charsets (we use inverted chars)
SCREEN= $4000 ; Position of the video matrix
SHIFTL= $CF00 ; x-shift, lowest 3 bits
SHIFTH= $CE00 ; x-shift, highest 3 bittid (multiplied with two)
POINTER= $033C ; Pointer to shift-table
VALUE= $033D ; Shift now
SPEED= $033E ; Shift change