25 Jun
1997
25 Jun
'97
11:40 a.m.
The Model I originally shipped without a numeric keypad. To the right
of the main keyboard was a rectangular keypad-size plaque reading "Radio
Shack TRS-80 Micro Computer System". The numeric keypad was added to
later models, and was available as a retrofit kit for around $50. With
the numeric keypad installed, the nameplate was moved to a horizontal
plaque above the keyboard.
The TRS-80 Model I lineage includes:
Model I, 4K, Level I BASIC
- This is a 3-piece system with the computer in the keyboard. It
includes the system keyboard/cpu, monitor, tape drive (actually a
rebadged regular Radio Shack portable cassette deck with no
modifications), and power supply brick. Level I BASIC is similar to
Tiny BASIC. I still have my Level I BASIC reference manual.
Model I, 16K, Level II BASIC
- The 16K and Level II upgrades went together. 16K is the maximum Model
I memory in the system unit (8x 4116 DRAMs). Level II BASIC is similar
to Microsoft BASIC/80 with functions added for things like the TRS-80's
128x48 memory-mapped monochrome graphics. Level II also added a
keyboard debounce routine--Level I machines were very difficult for
typists.
Other Upgrades:
- Expansion Interface
Matching silver color, acts as a monitor stand, connects to system unit
via ribbon cable. Contains dual floppy controller (WD chip), sockets
for an additional 32K (2 banks of 4116 DRAMs) for a system maximum of
48K, and a parallel connection. 16K ROM BASIC occupied the remainder of
the address space. The expansion interface also contains a card bay for
an RS-232 interface.
- RS-232 interface board
For expansion interface.
- Floppy drives
Single-sided single-density, approx. 90KB free space.
- Lower case upgrade
Provides lower case capability.
- Numeric keypad retrofit
As discussed above
Known TRS-80 Model I problems:
- Unreliable cassette interface. Radio Shack later released a
modification that improved this somewhat. The best option is a
third-party unit called the Data Dubber by Microperipheral Corporation
(I worked there!) that went in between the system unit and cassette and
squared the wave.
- Wonky, unbuffered connection to Expansion Interface. This went
through various modifications, and some cables you'll see have big
buffer boxes in the middle. Later Expansion Interfaces had built-in
buffering. Some bought third-party expansion interface clones from Lobo
and others. Be very careful if you get an Expansion Interface without a
cable. It might need the buffered cable, and it would be a pain to
manufacture.
- Bad data separator chip. The stock data separator was unreliable.
Most people replaced theirs with a third-party improvement such as
Percom's.
- Unreliable connection for the Expansion Interface-mounted RS-232
board. This board slipped over vertical post connections and never made
good contact. Most folks used third-party alternatives that worked off
the cassette port.
Kai
----------
From: Mr. Self Destruct
Reply To: classiccmp(a)u.washington.edu
Sent: Wednesday, June 25, 1997 4:14 PM
To: Discussion re-collecting of classic computers
Subject: Re: MSX, TRS-80, Colour Genie, etc.
On Wed, 25 Jun 1997, Scott Walde wrote:
No. They were originally known (and labelled) as
the TRS-80
Microcomputer
System. They later became known as the model 1
(Although I don't
think
they were ever labelled as such.)
Were there two different Model 1's? I have seen pictures of Model 1's
that don't look like my Model 1. (i.e. no numeric keypad)
Les
more(a)crazy.rutgers.edu
25 Jun
25 Jun
4:07 p.m.
On Wed, 25 Jun 1997, Kai Kaltenbach wrote:
The Model I originally shipped without a numeric
keypad. To the right
of the main keyboard was a rectangular keypad-size plaque reading "Radio
Shack TRS-80 Micro Computer System". The numeric keypad was added to
later models, and was available as a retrofit kit for around $50. With
the numeric keypad installed, the nameplate was moved to a horizontal
plaque above the keyboard.
The TRS-80 Model I lineage includes:
Model I, 4K, Level I BASIC
- This is a 3-piece system with the computer in the keyboard. It
includes the system keyboard/cpu, monitor, tape drive (actually a
rebadged regular Radio Shack portable cassette deck with no
modifications), and power supply brick. Level I BASIC is similar to
Tiny BASIC. I still have my Level I BASIC reference manual.
Level I BASIC _was_ Tiny BASIC.
Model I, 16K, Level II BASIC
- The 16K and Level II upgrades went together. 16K is the maximum Model
They wre available separately -- but a 4k Level II machine only left
about 1800 bytes of free RAM -- not a pretty sight (And yes, I've seen it!)
I memory in the system unit (8x 4116 DRAMs). Level II
BASIC is similar
to Microsoft BASIC/80 with functions added for things like the TRS-80's
128x48 memory-mapped monochrome graphics. Level II also added a
Amazing, though, how Big Five could use those graphics for the most
amazing video games (and produce sound from the cassette port to match)
-- it took the PC a couple of years to match it.
keyboard debounce routine--Level I machines were very
difficult for
typists.
Actually, the keybounce problem existed with Level II -- the keybounce
fix was a tape to read originally into a Level II box -- there was never
a fix for Level I (my own system the keybounce always came back -- I never
used the tape, it ate a K of RAM I needed -- when I made the mistake of
turning the keyboard upside down and dumping out the cigarette ashes ,
while they were there, apparently it smoothed the keyswitch operation
adequately). There was a second release of Level II BASIC that included
the debouncer in the 12K ROM.
Other Upgrades:
- Expansion Interface
Matching silver color, acts as a monitor stand, connects to system unit
via ribbon cable. Contains dual floppy controller (WD chip), sockets
for an additional 32K (2 banks of 4116 DRAMs) for a system maximum of
48K, and a parallel connection. 16K ROM BASIC occupied the remainder of
the address space. The expansion interface also contains a card bay for
an RS-232 interface.
Dennis Kitsz did once publish an upgrade to 48k that could be done in a
keyboard without the EI. I have no idea how many others built it, but I
never had a problem with the alleged memory speed problems from the EI
cable. Jerry Pournelle's gripes are another story.
- RS-232 interface board > For expansion interface.
Worked better than an Apple serial card from the era.
- Floppy drives
Single-sided single-density, approx. 90KB free space.
Geez, I remember spending $39.95 for my first 10-pack of SSSD 35-track
disks. Amazingly, I years later formatted one of them in a Tandy 2000
DSQD drive (call it five years later) with full verify and got two bad
tracks. Yeah, I should have hung onto the disk, put some data onto it,
and tried to read that data a year later. But I was about to throw away
the disk anyway, since it had shown errors on a Model 3.
- Lower case upgrade
Provides lower case capability.
I _still_ don't understand that trade-off between cost and utility. The
decision makers were gone before I joined the company in '80.
Known TRS-80 Model I problems:
- Unreliable cassette interface. Radio Shack later released a
modification that improved this somewhat. The best option is a
third-party unit called the Data Dubber by Microperipheral Corporation
(I worked there!) that went in between the system unit and cassette and
squared the wave.
It was more reliable than the cassette interfaces for the Apple or the Pet
ot the Atari. _All_ cassette interfaces are unreliable. How many people
used the cassette interface on an Apple for more than a week before they
gave up and got a disk drive? How many people used the cassette interface
on the Atari 400/800 for more than a day? Some TRS-80 users never felt
the need: it was not as unreliable as most of the competition. Many Color
Computer users noticed how much faster their cassette transfers were than
Commodore disk drives that they didn't upgrade until OS-9 showed up and
they _really_ needed disk drives.
- Wonky, unbuffered connection to Expansion Interface.
This went
through various modifications, and some cables you'll see have big
buffer boxes in the middle. Later Expansion Interfaces had built-in
buffering. Some bought third-party expansion interface clones from Lobo
and others. Be very careful if you get an Expansion Interface without a
cable. It might need the buffered cable, and it would be a pain to
manufacture.
Can't make excuses for this technically myself. That unbuffered cable
carrying RAM signals was flat-out stupid. But remember that when the
first machines were designed that the company (always retail driven) had
_no_ idea that the damned things would sell, it was an experiment. Hell,
Apple and Commodore had been advertising all year, and hadn't delivered
more than a few eval and review units when Tandy announced the TRS-80
Microcomputer System on 3 Aug 77 with 5,000 units already in the
warehouses -- idea was, since they didn't know if it would work, they had
5,000 stores -- if the silly things didn't move they'd figure out a way
to use them.
- Bad data separator chip. The stock data separator
was unreliable.
Most people replaced theirs with a third-party improvement such as
Percom's.
The one Percom used came out after the design was final.
- Unreliable connection for the Expansion
Interface-mounted RS-232
board. This board slipped over vertical post connections and never made
good contact. Most folks used third-party alternatives that worked off
the cassette port.
_Nothing_ was reliable in the Expansion Interface, ever. Not even the
clock. And the Model III came out about the time most of the problems
were solvable. Many companies phase out upgrades of systems that have
been superceded -- when's the last time MicroSlough actually fixed one of
the many problems that still exist in Windows 3.1?
--
Ward Griffiths
"America is at that awkward stage. It's too late to work within
the system, but too early to shoot the bastards." --Claire Wolfe
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