TRS-80 Color Computer - Origin and History

Origin and History

The TRS-80 Color Computer started out as a joint venture between Tandy Corporation of Fort Worth, Texas and Motorola Semiconductor, Inc. of Austin, to develop a low cost home computer in 1977.

The initial goal of this project, called "Green Thumb", was to create a low cost Videotex terminal for farmers, ranchers, and others in the agricultural industry. This terminal would connect to a phone line and an ordinary color television and allow the user access to near real-time information useful to their day-to-day operations on the farm.

Motorola's MC6847 Video Display Generator (VDG) chip was released about the same time as the joint venture started and it has been speculated that the VDG was actually designed for this project. At the core of the prototype "Green Thumb" terminal, the MC6847, along with the MC6809 Microprocessor Unit (MPU), made the prototype a reality by about 1978. Unfortunately, the prototype contained too many chips to be commercially viable. Motorola solved this problem by integrating all the functions of the many smaller chips into one chip, the MC6883 Synchronous Address Multiplexer (SAM). By that time in late 1979, the new and powerful Motorola MC6809 processor was released. The SAM, VDG, and 6809 were combined and the AgVision terminal was born.

The AgVision terminal was also sold through Radio Shack stores as the VideoTex terminal around 1980. Internal differences, if any, are unclear, as not many AgVision terminals survive to this day.

With its proven design, the VideoTex terminal contained all the basic components for a general purpose home computer. The internal modem was removed, and I/O ports for cassette storage, serial I/O, and joysticks were provided. An expansion connector was added to the right side of the case for future enhancements and program cartridges ("Program Paks"), and a RAM button (a sticker indicating the amount of installed memory in the machine) covered the hole where the Modem's LED "DATA" indicator had been. On July 31, 1980, Tandy announced the TRS-80 Color Computer. Sharing the same case, keyboard, and layout as the AgVision/VideoTex terminals, at first glance it would be hard to tell the TRS-80 Color Computer from its predecessors.

The initial model (catalog number 26-3001) shipped with 4K of Dynamic Random Access Memory (DRAM) and an 8k Microsoft BASIC interpreter in ROM. Its price was $399. Within a few months, Radio Shack stores across the US and Canada began receiving and selling the new computer.