My New TRS-80 Model 4
Dan Stangel
the almost-ergonomic keyboard, and the shiny silver label that reads "64K
RAM"... My new TRS-80. I just got it yesterday from a teacher who had
been compiling grades on Trash-80's since the late 70's, and only stopped
a few months ago when he wrote his own PC software. But a few questions:
1) Any interesting facts on this machine?
2) What were the differences in models from the Model 1 to whatever the
last model made?
3) Why is it that on every TRS-80 I've ever seen, when one turns up the
contrast & brightness all the way, one sees the same diagonal line
pattern?
4) What sort of neat-o things can I do with it (Other than set drinks on
it, abuse it, take it apart, and, of course, admire its spartan yet
excitingly well planned engineering)
Dan S .
Benicia, California, USA
Jeffrey Thomas Sheldon
: RAM"... My new TRS-80. I just got it yesterday from a teacher who had
: been compiling grades on Trash-80's since the late 70's, and only stopped
: a few months ago when he wrote his own PC software. But a few questions:
Stop it...I think I'm going to cry...
: 1) Any interesting facts on this machine?
Yeah, it's one of the only machines that could recover my poor program I
wrote back in 7th grade computer literacy that pulled my grade from a
proposed F to a solid B in one quarter. It was the best program she ever
got on a TRS-80. The younger generations hacked it to hell, but they
knew a classic when the saw it (or so I'm told).
: 4) What sort of neat-o things can I do with it (Other than set drinks on
: it, abuse it, take it apart, and, of course, admire its spartan yet
: excitingly well planned engineering)
You could give it to someone who's been looking for one for YEARS and
never been lucky enough to get one <sniff>. Poor me. :)
Enjoy it! It gave me some of the best years of my life! I'm sure it
still would too....I just need to keep my eyes open on the local scene.
-Jeff
--
.sig
Scott Statton N1GAK
Dan Stangel <sta...@netcom.com> wrote:
[ ... I got a new TRS-80 .. ]
>2) What were the differences in models from the Model 1 to whatever the
> last model made?
Know your Trash 80s.
TRS-80 Model 1 --
o 1.8~ MHz Z80;
o 4K ROM BASIC -- Rumour says it was Li Chen's Tiny Basic with
floating point crocked in at the last minute.
o 4K Dynamic RAM (8K and 16K versions were announced and
many 16K models were shipped)
o Direct knock off of the Polymorphics video card, 64x16 7-bit
memory; could display uppercase text or each character
position could be a glyph with six huge "pixels". BASIC had
pixel set/reset commands.
o I/O Bus was a (barely/inadequately) buffered version of the
Z80 pinout.
o Memory mapped keyboard
o Released for $599 for the 4K/4K version
o Awful 250 bps cassette drive that used more-or-less square
waves to record 500 "clicks" per second on the tape -- one
clock click followed by an optional data "click"; Level 2
BASIC (12K ROM) doubled the speed and halved the
reliability. Whole thing was done in software -- the
"demodulator" was an op-amp based "click" detector that
would set a flip flop that could be read/reset by software;
o Expansion was via the "TRS-80 Expansion Interface" that
could hold up to 32 K of memory; a second Lame casette
interface; a parallel printer interface; a 25 Hz interrupt;
single density disk controller 87.5K per disk (35 track; 10
sector; 256 byte).
Model 2 -- I dont know much about this one -- it was very expensive;
had a nice 80x24 display; the most likely sold configuration included
8" floppy drives;
Model 3 -- Desktop version of Model 1 -- increased CPU speed to 2.7ish
MHz; added lower case; up to 48 kilobytes of memory on the CPU board;
had a different (incompatible, better buffered) I/O bus. On board
parallel; Many systems sold with built-in serial port (that was
actually an option); 30Hz RTC interrupt that was locked to the video
circuitry; space inside for two Shugart 5" full-height auto-dealigning
drives. Offered a 1500 bps cassette interface that used a more
fsk-like signal -- almost, but not quite, reliable. Used a "double
density" disk controller -- 180K diskettes (40 tracks 18 sectors 256 bytes)
Model 4 -- Upgraded Model 3 -- added an 80x24 video mode; had a
bizarre memory mapping that allowed you to have up to 128K of
bank-switched memory.
Model 4P -- Luggable version of Model 4.
Model 4D -- Model 4 with double-sided disk drives (360K).
Model 16 -- 68000 based box; ran Xenix
I remember there was also a model 12;
>3) Why is it that on every TRS-80 I've ever seen, when one turns up the
> contrast & brightness all the way, one sees the same diagonal line
> pattern?
That's vertical retrace -- horizontal keeps running -- any monitor
will show that if you have enough range in the controls.
>4) What sort of neat-o things can I do with it (Other than set drinks on
> it, abuse it, take it apart, and, of course, admire its spartan yet
> excitingly well planned engineering)
Find the Orchestra-80 card. It's a pair of DACs and you can have some
fun with it.
Scott Statton - N1GAK - Mountain View, CA - sco...@cluon.com
GE/CS d-- H+(++) s+:++ g+ p1 au--(----) a28 w+ v++(-) C++++ US++++$ P+
L- 3- E++ N++ K W--- M+ V -po+ Y+ t+ 5 j+ R- G' tv b++ !D B(-) e
u+ h++ f+ r+++ n+ y+++(*)
Dan Stangel
: : Ahhh... That handsome white plastic case, the pert little CRT built in,
: : RAM"... My new TRS-80. I just got it yesterday from a teacher who had
: : been compiling grades on Trash-80's since the late 70's, and only stopped
: : a few months ago when he wrote his own PC software. But a few questions:
: Stop it...I think I'm going to cry...
: : 1) Any interesting facts on this machine?
: Yeah, it's one of the only machines that could recover my poor program I
: wrote back in 7th grade computer literacy that pulled my grade from a
: proposed F to a solid B in one quarter. It was the best program she ever
: got on a TRS-80. The younger generations hacked it to hell, but they
: knew a classic when the saw it (or so I'm told).
So what did the program DO?
: You could give it to someone who's been looking for one for YEARS and
: never been lucky enough to get one <sniff>. Poor me. :)
: Enjoy it! It gave me some of the best years of my life! I'm sure it
: still would too....I just need to keep my eyes open on the local scene.
Gee, I'd love to send you my TRS-80 model 3, but I don't think UPS would
take it, considering what poor shape its in. :(
rhaw...@iastate.edu
Scott Statton N1GAK <sco...@cluon.com> wrote:
> o Memory mapped keyboard.
a generous turn of phrase. the keys were connected to the
address lines and their input address (or was it an io port; i forget),
and the processor scanned them. If you hit the keyboard a lot, even
when it wasn't looking for input, it visibly slowed the machine.
> o Expansion was via the "TRS-80 Expansion Interface" that
> could hold up to 32 K of memory; a second Lame casette
> interface; a parallel printer interface; a 25 Hz interrupt;
> single density disk controller 87.5K per disk (35 track; 10
> sector; 256 byte).
but it could also drive disks with more tracks quite well
>Model 2 -- I dont know much about this one -- it was very expensive;
>had a nice 80x24 display; the most likely sold configuration included
>8" floppy drives;
4mhz z80, with an 8" drive mounted next to the display
>Model 3 -- Desktop version of Model 1 -- increased CPU speed to 2.7ish
^^^^^
it put it all into a single housing; it was about the same size. Also,
most model I's could be run at at least 2.5 with an extra oscillator
>MHz; added lower case; up to 48 kilobytes of memory on the CPU board;
^^^^^^^^^^^^^^^^
the keyboard was lower case to start with. the character generator was
also lower case. You could solder another 2102 (1kx1 static ram, about
$1.25) to a model 1, cut a trace, and add two wires to
the model 1 and get lower case (without descenders).
>actually an option); 30Hz RTC interrupt that was locked to the video
>circuitry; space inside for two Shugart 5" full-height auto-dealigning
>drives. Offered a 1500 bps cassette interface that used a more
>fsk-like signal -- almost, but not quite, reliable. Used a "double
>density" disk controller -- 180K diskettes (40 tracks 18 sectors 256 bytes)
--
R E HAWKINS
rhaw...@iastate.edu
--
R E HAWKINS
rhaw...@iastate.edu
--
R E HAWKINS
rhaw...@iastate.edu
David Librik
>In article <3h8ekv$a...@cluon.cluon.com>,
>Scott Statton N1GAK <sco...@cluon.com> wrote:
>> o Memory mapped keyboard.
> a generous turn of phrase. the keys were connected to the
>address lines and their input address (or was it an io port; i forget),
>and the processor scanned them. If you hit the keyboard a lot, even
>when it wasn't looking for input, it visibly slowed the machine.
You're kidding, right? I never noticed this. In fact, I don't even
understand how it could happen.
The way the TRS-80 keyboard worked was that it "shorted" the address
lines to the data lines, "across" the keyboard contacts. So when
you scanned address 3800H, you got a byte back which contained bits from
whether the keys @ A B C D E F G were down (in that order). At 3801H
you got H I J K L M N O, and on through 02H, 04H, 08H, 10H, etc. Note
that if you went for "odd" addresses you got odd results, and there were
places you could scan to tell if (say) BREAK and A were being both held
down.
One great advantage to this scheme was that it made keychords very easy,
and most TRS-80 games used the keyboard as control device. Apple 2 games
never could do this and generally had very crippled keyboard control.
But because it took no processing power to handle keypresses -- when the
key went down, NOTHING happened except an address line bit & a data line
bit were connected (you had to scan the address line to actually tell the
key had been hit) -- the machine did not slow down when you pressed keys.
It took processing power to detect and handle keypresses, of course, but
since there were no interrupts for keypresses then simply hitting the
key did nothing to the CPU. You had to scan the keyboard-matrix yourself
or call the ROM Get-A-Key subroutine. There was, therefore, no typeahead.
- David Librik
lib...@cs.Berkeley.edu
rhaw...@iastate.edu
David Librik <lib...@netcom.com> wrote:
>>If you hit the keyboard a lot, even
>>when it wasn't looking for input, it visibly slowed the machine.
>You're kidding, right? I never noticed this. In fact, I don't even
>understand how it could happen.
Nope, try one and find it. Even just list a program and repeatedly hit
massive numbers of keys; you'll notice the slowdown in the scroll.
>But because it took no processing power to handle keypresses -- when the
>key went down, NOTHING happened except an address line bit & a data line
>bit were connected (you had to scan the address line to actually tell the
>key had been hit) -- the machine did not slow down when you pressed keys.
>It took processing power to detect and handle keypresses, of course, but
>since there were no interrupts for keypresses then simply hitting the
>key did nothing to the CPU.
Exactly where the problem came in. It had to scan for the break key
while doing anything else. If you wrote your own machine code, i
excpect it was another story. But while BASIC had control of the
machine, there was constant scanning.
Robert.B...@cdc.com
> From: sta...@netcom.com (Dan Stangel)
> Ahhh... That handsome white plastic case, the pert little CRT built in,
> the almost-ergonomic keyboard, and the shiny silver label that reads "64K
> RAM"... My new TRS-80. I just got it yesterday from a teacher who had
> been compiling grades on Trash-80's since the late 70's, and only stopped
> a few months ago when he wrote his own PC software. But a few questions:
>
> 1) Any interesting facts on this machine?
What do you want to know?
> 2) What were the differences in models from the Model 1 to whatever the
> last model made?
TRS-80 Model I:
Z-80 CPU, <2 MHz, 4 KB RAM, tape interface, printer interface. The motherboard
was under the keyboard. The monitor was a modified RCA black and white TV. It
had an external power supply. The 4 KB chips could be replaced with 16 KB chips
(it cost me over $400 for those things).
With the expansion interface (E/I), you could add up to 32 KB more RAM (for a
total of 48 KB RAM), up to 4 floppy drives. The RS-232 interface was a board
that fit in the E/I (cost about $100).
The first floppies were 5 1/4-inch, 35 track, single sided, single density.
You could replace the floppy controller for a double-density one. That
wonderful TRS-DOS (albeit buggy) supported 35-, 40-, and 80-track drives.
TRS-80 Model II:
Z-80 CPU, ??? MHz, 8-inch floppy drives. This was the business machine. I don't
know a whole lot about it. The keyboard was separate from the monitor/computer
unit.
TRS-80 Model III:
Z-80 CPU, ??? MHz, 48 KB RAM, 2-5 1/4-inch floppy drives (single-sided,
double-density). All-in-one unit.
TRS-80 Model 4 (dropped the Roman numerals):
Z-80A CPU, 4 MHz, 64 KB RAM (expandable to 128 KB), 2-5 1/4-inch floppy drives
(single-sided, double-density), built-in speaker. These floppies were the old
full-height drives. I removed mine and replaced them with 4 of the half-height
double-sided, double-density, 80-track drives (720 KB each).
TRS-80 Model 4P:
Portable Model 4 (30 pounds). This is the machine that looks like a sewing
machine. I have one of these sitting on my desk at home. My wife still uses it
to do our budget. I removed the 2-5 1/4-inch drives (SS,DD) and replaced them
with 2-3 1/2-inch DS,DD drives. I have a 20 MB external SCSI hard drive.
XLR8R (accellerator):
Small board that plugged into the CPU socket of the Model 4 (maybe the III).
Contained a Hitachi HD64180 (I think) CPU (this is equivalent to the Z-180),
7.144 MHz. With one of these, you could have a TRS-80 with 3 serial ports and
384 KB RAM. My 4P is accellerated.
HI-RES graphics board:
32 KB RAM graphics board for 640 x 256 (I think) graphics. Whatever it is, I
know that it's better than CGA resolution (but monochrome).
> 3) Why is it that on every TRS-80 I've ever seen, when one turns up the
> contrast & brightness all the way, one sees the same diagonal line
> pattern?
Every mono monitor I've ever seen does that.
> 4) What sort of neat-o things can I do with it (Other than set drinks on
> it, abuse it, take it apart, and, of course, admire its spartan yet
> excitingly well planned engineering)
What software do you have? What do you want? The TRS-80 had BASIC, FORTRAN,
COBOL, Pascal, C, Forth, APL, JCL, and maybe a few other languages.
Andrew Clegg
" writes:
> --
> R E HAWKINS
> rhaw...@iastate.edu
>
> --
> R E HAWKINS
> rhaw...@iastate.edu
>
> --
> R E HAWKINS
> rhaw...@iastate.edu
>
Do you *really* need three sigs?
Andrew.
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