💾 Archived View for uscoffings.net › retro-computing › systems › Tandy › oldskool › txcadd.txt captured on 2023-09-28 at 19:08:33.

View Raw

More Information

⬅️ Previous capture (2023-07-10)

-=-=-=-=-=-=-

I use a Tandy 1000TX at work set up as a low-cost CADD
system.  It's not blindingly fast (see the comparitive times
later in this message), but works pretty well.  I have the
following items installed:

Everex 2400 baud internal modem set to COM1 (IRQ4)

Logitech Ergonomic Serial Mouse using the built in serial
port, set to COM2 (IRQ3)

A Tandy hardcard where I replaced the controller with an OMTI
5527T and reformatted to 32 megs - drive is a Miniscribe 8438
Set motherboard dip switch #2 to OFF, and the controller
automatically configures itself to IRQ5, and can co-exist on
IRQ5 with the internal video (if you use it).

A MicroMainframe 5150T EMS board populated to 2 megs with 100
nano-second chips.  You don't need chips this fast, I just
stumbled accross them at a time when no-one had any chips
available.  I've never used more than 736K at once, although
I just bought a new program that recommends a 1 meg ram disk.
The EMS board does not use a hardware interrupt.

An Everex EV657-1 super EGA video board.  This board supports
640 x 350, 640 x 480, and 800 x 600, all at 16 colors, but
does not support the other VGA modes.  You have to run a
memory resident utility to get 640 x 480, and 800 x 600
requires program specific drivers.  This is the mode I use
with Generic Cadd Level 3.  This board is set to the non-
maskable interrupt (NMI).  Turn motherboard switch #1 to OFF
when using an EGA or VGA board.  The Hercules emulation is
set to OFF on the board, and it auto-switches between the
three hi-rez modes without any problems.

The Everex board also has a parallel port on it.  I have the
parallel port set to address 0278-027F, and IRQ7.  Also turn
off motherboard switch #4, and the system will allow the
normal printer port to function as PRN or LPT1, and the
second port on the video board to function as LPT2, with both
of them operating on IRQ7.

The Everex board's parallel port drives a Roland DXY990 11"
x 17" plotter I bought through mail order three weeks ago on
closeout.

A Microway 287-12 turbo coprocessor.  This is a math chip and
clock circuitry to run the 80287 at 12 mhz, whereas the
normal circuitry runs the math chip at 5.33 mhz.  I built a
small relocation board because this 287 turbo didn't clear my
hardcard.

My monitor is an NEC MultiSync II (not the 2a).  The controls
are all right up front, and they allow you to expand the
disply right out to the edges of the bezel.  I'm very happy
with it.

The 1000TX has a small quirk when used with some EGA and VGA
cards.  It seems that pressing control-alt-delete on most
machines cause a so-called "warm boot", where the system
bypasses the memory checks (much quicker).  The 1000TX on the
other hand does a "cold boot" where it includes the memory
check.  Hitting control-alt-delete confuses the video card,
and you don't get a reliable reset.  There is a set of two
TSR's, in a file called RB1000.arc, in one of the DL's here,
that neatly fixes this by using the right shift key and the
print key to do a real warm boot on the TX.  (The left shift
and print keys still do a print screen.)  It works, and the
video card doesn't get confused, and it's quicker than
control-alt-delete.

I also run two TSR's to boost speed:

Rambios.arc:  This utility relocates the video board BIOS
code into RAM.  I downloaded it from the Everex bulletin
board @ (415) 683-2984.
 
Qfresh.com:  This is the utlity generated by a program that
analyzes and resets the memory chip refresh rate
(CALCQF.arc).  It has no measurable effect on the Cadd
program screen redraws, but other commands run perceptably
faster, including speeding up hard drive access.  Be careful,
as this program drives bus mice crazy, changing the
resolution, but serial mice are unaffected.

Save your money on the video upgrade.  If you put in an EGA
or VGA card, you have to put the jumper back in to avoid a
memory address conflict between the video upgrade and the
memory on the video board.  Installing the EGA or VGA board
dis-arms the internal video (along with turning motherboard
switch #1 to OFF), and gives you your full 640K of base
memory.

Find and run a program called Thrasher (THRASH.arc).  It
measures the optimum setting for the Buffers command in you
config.sys file.  This dramatically speeds up disk access
without the conflict potential of many disk caching programs.
Mine is set to Buffers=20.

Last, make sure that you load enough TSR's, and config.sys
commands so that your free memory is no more than 592K.  Use
CHKDSK.com (a DOS command) to verify this.  I ran into a
problem with Generic Cadd and the Micro-Mainframe EMS
driver, conflicting with the Tandy BIOS.  It seems that if
you have more base memory available than 592K, the programs
can't locate the EMS properly.  I found this when I first got
the EMS board, and Generic CADD reported 65,000 bytes
available for drawing memory, instead of the 2 megs I just
installed.  It seems that at the time the EMS board was
designed, they didn't allow for EGA cards or video expansion
in the 1000'S and assumed that at least 16K for video and 47K
for DOS would always be used.  This along with the EMS driver
brought the maximum leftover memory down to 592K or so.

Comparitive times to do a zoom all command in Generic Cadd on
a test drawing:

TX without co-processor            55.2 seconds
TX with co-processor @ 5.33 Mhz    16.4 seconds
TX with Turbo 287-12               13.2 seconds
Compuadd 386-20 - no co-pro        19.7 seconds
Tandy 4000LX with co-pro            4.4 seconds

800 x 600 takes about 0.2 seconds longer than 640 x 480.

Whew!