High-resolution graphics for the TRS‑80

written by Matthew Reed

Unlike many competing computers, the TRS‑80 Model I lacked any form of built-in high-resolution graphics. Although some TRS‑80 compatible computers, such as the LNW80, offered high-resolution as a feature, the only graphics possible with the Model I were relatively low-resolution 128 by 48 block graphics. The many games written for the Model I made good use of these block graphics, and Radio Shack never made high-resolution a standard feature of the Model I, III, or 4. Several companies created products to address this deficiency, with some becoming more popular than others.

Model I

The Model I text screen was 64 by 16 characters with a character matrix of 6 by 12 pixels, meaning an underlying graphics resolution of 384 by 192. Although there were many “do-it-yourself” Model I high-resolution projects (such as the one detailed by Dennis B├íthory-Kitsz in his book The Custom TRS‑80), there were relatively few commercial products and they came fairly late in Model I development. The fact that the products were uncommon also meant that they enjoyed limited software support.

Name Company Date Initial price Resolution Text overlay Installation
80-GRAFIX Programma International 1980 $149.95 384 by 192 (indirectly through character redefinition) not applicable minimal soldering
SubLOGIC 50/T80 SubLOGIC 1980 unknown 256 by 240 no plug-in
Mikeegraphic Graphic System Mikee Electronics 1981 $340.00 384 by 192 yes soldering and trace cutting

Model III

Although the Model III text screen remained at 64 by 16 characters, the character matrix increased to 8 by 12 pixels. This meant that the graphics resolution also increased to 512 by 192. Radio Shack developed an “official” high-resolution add-on that used its own video controller to achieve higher resolution. Despite its official status, few programs supported it. Software support remained a problem for all of the add-ons: only the Grafyx Solution managed a significant number of compatible programs.

Name Company Date Initial price Resolution Text overlay Installation
80-GRAFIX Micro-Labs 1981 $169.95 512 by 192 (indirectly through character redefinition) not applicable plug-in, with no soldering
Mikeegraphic Graphic System Mikee Electronics 1982 $340.00 512 by 192 yes soldering and trace cutting
Grafyx Solution Micro-Labs 1982 $299.95 512 by 192 yes plug-in and micro-clip connections
Radio Shack High-Resolution Board Radio Shack 1982 $369.95 640 by 240 no professional installation required

Model 4

Unlike the Model I and III, the Model 4 was designed to support high-resolution even though it was never offered as a standard feature. The Model 4 motherboard had a built-in graphics connector to support a high-resolution add-on board. The Radio Shack Model 4 High-Resolution Board and the Model 4 Grafyx Solution were software compatible with each other (but not compatible with the Model III Grafyx Solution). This meant that most Model 4 high-resolution software worked with either board.

High-resolution add-ons (especially the Grafyx Solution) became a very popular item, and this led to a wide range of high-resolution programs being written for the Model 4.

Name Company Date Initial price Resolution Text overlay Installation
Radio Shack High-Resolution Board Radio Shack 1983 $249.95 640 by 240 possible using undocumented port professional installation required
Grafyx Solution Micro-Labs 1984 $199.95 640 by 240 yes plug-in and micro-clip connections
Categories: Graphics


Mark McDougall says:

There was another Model I hires graphics board – the PCG-80. It allowed you to reprogram all 256 characters in the TRS‑80 character set. For re-programming, it mapped the character memory into screen RAM, IIRC in 4 banks of 64 characters at a time.

I wrote a program that produced a lower case character set for our Model I. It was the first thing I ran each time I powered-on and booted NEWDOS/80. I also converted a few assembly language arcade games to hires, including Jungle Raiders and Star Cresta.

I have a copy of Jeff Vavasour’s Model I emulator that someone else patched for PCG-80 support. I did have these two games running on the emulator in the past. I also believe I have the documentation for the PCG-80 lying around somewhere too.

Mark McDougall says:

I just fired up the emulator again and found that there were a handful of other games converted to hires for this board, including ZChess, Sargon II, Hoppy, Black Hole, Star Bird & Time Trek. There was also a graphics basic and a program for editing characters.

David Sutherland says:

Perhaps just one additional chart could be added which would show: 1) all TRS‑80 “clones” and 2) if any of the systems are compatible with each other the charts would show it.

Those charts are really good at quickly understanding what’s-what. Thanks again Matthew!

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