TRS-80 Color Computer - Differences From Earlier TRS-80 Models

Differences From Earlier TRS-80 Models

The Color Computer, with its Motorola 6809E processor, was a radical departure from the Z80-based TRS-80 Models. Indeed the "80" in "TRS-80" stood for "Z80". 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 Z80-based predecessors, the CoCo shipped with BASIC, but in this case Tandy licensed Microsoft BASIC. As with the Z80 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. Additional ROMs such as JDOS (Copyright J&M Systems) were available to enable the use of double sided disc drives.

The CoCo, which could display eight colors at once, was designed to be attached to a color television set, whereas the Z80 machines used monochrome computer monitors, often built into the 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. Tandy also released a Multi-Pak Interface which allowed switching quickly among four cartridges mounted at the same time. This was similar in concept to the Model I's Expansion Interface.

Unlike some Z80 models, the CoCo did not come with a built-in floppy drive. The CoCo was designed to save and load programs and data from a standard audio cassette deck. Although slow (though at an average of 1500 bit/s it was faster than the Commodore 1541) and sometimes unreliable, this made the CoCo more affordable as a home computer. Tandy eventually offered a floppy disk drive controller for the CoCo as a cartridge. Both the CoCo and earlier TRS-80s shared the WD17xx series floppy disk controllers and 35 (later 40) track industry-standard floppy drives.

Even with the add-on floppy drive, the CoCo did not have a true DOS until third-party operating systems such as TSC FLEX9 (distributed for the CoCo by Frank Hogg Laboratories) 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.

Some non-program expansion cartridges included a sound/voice synthesiser (which led to the CoCo being used as an accessibility device for the disabled), 300 baud modem pak, RS232 pak, a hard drive controller, stereo music adapter, floppy disk controller, input tablet, and other accessories. The CoCo was the first Tandy computer to have a mouse available for it.