Games - TRS-80 Color Computer

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	Games - TRS-80 Color Computer

The Radio Shack TRS-80 color computer (also called Tandy Color Computer, or CoCo) was a home computer based around the Motorola 6809E processor and part of the TRS-80 line.

Origin and history

The TRS-80 Color Computer, often referred to as CoCo by its users, started out as a joint venture between Fort Worth based Tandy Corporation and (then) Austin based Motorola Semiconductor, Inc. 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 TV 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 MC6808 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 and, together, the SAM, VDG, and 6809 are combined. The AgVision terminal is 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, 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 was. On July 31, 1981, 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, which was catalog number 26-3001, shipped with 4K of Dynamic Random Access Memory (DRAM) and an 8k Microsoft BASIC interpreter on an internal ROM. Its price was $399. Within a few months, Radio Shack stores across the US and Canada began receiving and selling the new computer.

Differences from earlier TRS-80 models

The Color Computer was a radical departure from the Z80-based TRS-80 Models I/II/III/4/4p with its Motorola MC6809E processor. Indeed the "80" in "TRS-80" stood for "Z-80". For a time, the CoCo was referred to internally as the TRS-90 in reference to the "9" in "6809". However this was dropped and all CoCos sold as Radio Shack computers were called TRS-80 in spite of the processor change.

Like its Z-80 based predecessors, the CoCo shipped with BASIC, but in this case was a Microsoft BASIC. The CoCo was designed to be attached to a color television set, whereas the Z-80 machines were either connected to an external monochrome monitor or had their monitor built in to their case. The CoCo also featured an expansion connector for program cartridges (mostly games) and other expansion devices, such as floppy disk controllers and modems. In this way it shared some similarity to the Atari 2600, Atari 400/800 and other cartridge-capable game consoles and computers.

Like the Z-80 systems, there were multiple "levels" of BASIC. In the case of the CoCo they were the standard Color BASIC and Extended Color BASIC. Beyond that, Disk Extended Color BASIC came with the floppy controller, and on the CoCo 3, "Super" Extended Color BASIC extensions were added by Microware.

Both TRS-80 systems (eventually) offered floppy disk drives. Both the CoCo and earlier TRS-80's shared the WD17xx series floppy disk controllers and 35 (later 40) track industry-standard floppy drives. The CoCo did not have a true DOS until operating systems such as TSC FLEX (distributed for the CoCo by Frank Hogg) and Microware's multi-user, multi-tasking OS-9 were available. However a disk-based CoCo did contain Disk Extended Color BASIC on an internal ROM in the controller cartridge that gave the BASIC user the ability to save and load programs from the disk and store and retrieve data from disk in various ways.

[ Visit the complete Wikipedia entry for TRS-80 Color Computer ]

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