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List (Unformatted): AMDOS.INFO
This file must be called "AMDOS.INFO" on your computer.
AmDOS 3.5
Copyright 1985 Gary B. Little
AmDOS 3.5 (Amateur Disk Operating System version 3.5) is an
Apple II program for initializing 3.5-inch UniDisk disks in such
a way that they will boot the DOS 3.3 operating system and work
properly with it. To use it, first LOAD your Applesoft greeting
program into memory and then BRUN the program called AMDOS INIT.
After you press the space bar to clear the "user-supported
program" notice, enter the slot and drive number of the disk to
be formatted and then the name of the greeting program; once you
do this, insert the disk to be formatted and press "F" to start
the process. Formatting takes approximately one minute.
AmDOS logically divides a formatted 3.5-inch disk into two
discrete 400K volumes; there are 50 tracks per volume and 32
sectors per track. Use the ",D1" and ",D3" drive parameters (as
well as a slot parameter, if necessary) with your DOS 3.3
commands to select the first and second volumes of drive 1. Use
",D2" and ",D4" to select the first and second volumes of drive
2. For example, to catalog the second volume on drive 1, use the
command "CATALOG,D3". As with standard DOS 3.3, if you don't
specify a slot or drive parameter, the most recently specified
value is implicitly used.
Compatability
With AmDOS installed, the INIT command is disabled. If you need
to initialize a 5.25-inch floppy disk, you will first have to
boot a disk that contains a standard copy of DOS 3.3. To re-
install AmDOS after you've loaded standard DOS 3.3, boot from a
previously formatted 3.5-inch disk.
AmDOS makes use of two data areas in the high end of memory:
$BD12-$BD14 and $BEAF-$BFA7. These areas must not be used by any
DOS 3.3 "patches" you might install. AmDOS also uses a 512-byte
I/O buffer at $9AF9-$9CF8; the standard DOS 3.3 file buffers are
installed just below this area. AmDOS sets MAXFILES = 2 (two
file buffers) when it boots up; this means that HIMEM (the top
of memory pointer) initially contains $9653. The DOS 3.3 default
of MAXFILES = 3 is not used because that would result in a HIMEM
of $9400, instead of the usual $9600, and any program that used
the area from $9400 and $95FF for data storage would not work
properly because the file buffer area would be overwritten. Such
programs erroneously assume that HIMEM is always $9600.
If you want to run a program that expects three file buffers to
be active (there are not many programs like this), enter the
DOS 3.3 "MAXFILES 3" command before running it.
You can use a slightly-modified version of the FID utility
program on the DOS 3.3 system master disk to transfer files to
and from AmDOS-formatted 3.5-inch disks. Here are the steps to
follow to make the modifications to a copy of FID:
]UNLOCK FID
]BLOAD FID
]CALL -151
*0973:B5
*09BF:B5
*11ED:4C 89 16
*1414:B1
*1689:8D 31 19 B9 8B 19 8D 32 19
*1692:B9 8C 19 8D 33 19 0D 32 19
*169B:0D 31 19 4C F2 11
*3D0G
]BSAVE FID,A2051,L4686
The modified FID will still work properly with standard DOS 3.3
and with 5.25-inch floppy disks.
Memory Map
Here is a memory map showing the arrangement of buffers below
the main AmDOS code and data area beginning at $9D00:
^ ^
| AmDOS (DOS 3.3) |
| code and data area |
-------------------------- <--- $9D00
| [unused] |
-------------------------- <--- $9CF9
| AmDOS 512-byte buffer |
-------------------------- <--- $9AF9
| |
| File buffer #1 |
| |
-------------------------- <--- $98A6
| |
| File buffer #2 |
default | |
HIMEM ---> -------------------------- <--- $9653
| |
| File buffer #3 |
| (only if MAXFILES = 3) |
-------------------------- <--- $9400
AmDOS 3.5 is a user-supported program. Try it for 30 days and if
you find it useful, send $15 (U.S.A. funds) or $20 (Canadian
funds) to Gary B. Little, #210 - 131 Water Street, Vancouver,
British Columbia, Canada, V6B 4M3 (Telephone: (604) 681-3371).
Otherwise, pass your copies along to others or erase them.
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