The Electric Crayon

written by Matthew Reed

Electric Crayon advertisement

Percom advertisement from the April 1980 issue of 80 Microcomputing

Back in the late 1970’s, the Apple II and the TRS-80 Model I were competitors for computer sales. One advantage the Apple II had over the Model I was the ability to display color graphics. One of the first Model I products to address this deficiency was the Percom Electric Crayon. Percom introduced the Electric Crayon in December 1979 for a base price of $249.00. It was featured on the cover of the January 1981 issue of 80 Microcomputing.

The Electric Crayon was a small (12 inch wide by 9 inch deep) box which output a composite video signal that could drive either a monitor or a television set. It connected directly to the TRS-80 printer port and was controlled using EGOS, a ROM-based operating system. EGOS was directly programmed using single character commands. Virtually unique among TRS-80 color add-ons, the Electric Crayon did not use the TMS9918 graphics chip and did not support sprites.

Ten video modes were available, including two semigraphics modes and eight graphics modes, but only two of them were possible with the default 1K of video memory. All ten modes were possible if the video memory was upgraded to a full 6K (Percom charged $29.95 for each kilobyte).

The maximum resolution was 256 by 192 and eight colors were possible: green, yellow, blue, red, buff, cyan, magenta, and orange. But only four colors were allowed at the higher resolutions and only two at the highest resolution. In semigraphics modes, a built-in character generator helped with displaying text.

The Electric Crayon was quite an impressive peripheral. Harold Mauch, the president of Percom, described it as “a complete, self-contained control computer with provision for 1K-byte of on-board program RAM, an EPROM chip for extending EGOS and a second dual bidirectional 8-bit port – over and above the dual I/O computer port – for peripherals.” But most of that promise remained untapped. Percom sold a few programs for the Electric Crayon but the software and games that might have taken full advantage of its features were never written.

Categories: Graphics, Hardware


John W. Linville says:

I would really like to own one of these. If you have one and are interested in selling it, then please contact me!


Ken Gregg says:

I had one of the Percom Electric Crayon 6K units attached to my TRS-80 Model I back in the early 1980s. It cost a total of $310. While I was working on my CS degree, I used it to test out my graphics algorithms in (relatively) hi-res color before porting my code over to the university’s Apple II system where the projects had to be demonstrated. I also used the Crayon when I was giving talks – essentially presenting “PowerPoint-esque” slides on a large color monitor, before PowerPoint was a thing.

I wish I had hung onto it, but ended up donating everything in 1985 to make room for a new generation of gear. Now that I have room for both new and old, I’m pining for it again. If anyone has a pointer to the manual, I would be interested in revisiting the EGOS commands.