The CHROMAtrs

written by Matthew Reed

CHROMAtrs advertisement

CHROMAtrs advertisement from the November 1982 issue of 80 Micro

The most popular of the TRS‑80 Model I and Model III color add-ons was the CHROMAtrs, introduced by South Shore Computer Concepts in 1982. It was available in several different configurations:

  • a kit without case or power supply cost $99.00
  • a kit with case and power supply cost $129.00
  • a fully-assembled and tested unit cost $169.00

The CHROMAtrs came with a full 16K of memory, allowing the highest resolution to be displayed without any further memory expansion. Each unit supported both the Model I or Model III and would work with either computer using the proper cable. The Model III cable would also work with the Lobo MAX‑80 with a few minor modifications.

The core of the CHROMAtrs was the Texas Instruments TMS9918A graphics controller, the same chip used by the ColecoVision, the TI-99/4, and a number of other systems at the time. It supported a total of four video modes: one 40 by 24 text mode and three graphics modes. The maximum screen resolution was 256 by 192, the same as the TRS‑80 Color Computer and nearly as high as the 280 by 192 of the Apple II. Sixteen colors (including transparent) were possible on a color television or eight shades of gray on a black and white television.

Another interesting feature of the CHROMAtrs (actually of the TMS9918A controller) was prioritized sprites. Up to 32 sprites could be displayed on screen at once and all display details were automatically handled by the controller. The sprites could even pass in front of one another, with the higher priority sprites overlapping the lower priority ones.

Two features unique to the CHROMAtrs among TRS‑80 color add-ons were sound generation and joystick support. The sound, although fairly simple, could be heard either on the television or through a separate RCA jack. Two joystick connectors supported Atari joysticks or paddle controllers.

Each CHROMAtrs came with a software driver, a version of LOGO, and a game to help show off the color graphics. South Shore sold a number of CHROMAtrs programs, including CHROMA BASIC, a very impressive color graphics BASIC which originally cost $30 but soon was bundled with the CHROMAtrs. Upon request, they would also send a list that they maintained of third-party CHROMAtrs programs. By the end of 1983, South Shore changed their name to Micro Control Systems, Inc., but they continued to sell the CHROMAtrs.

Although there was more software written for the CHROMAtrs than any other TRS‑80 color add-on, it still remained an intriguing niche option. There was never a “killer app” written for the CHROMAtrs that might have helped to drive wider adoption.

Categories: Graphics, Hardware