The CoCo3 came with 128K RAM, an analog RGB video port, enhanced 640x192 graphics capability, a 64-color palette and much more. (All ports contained on the CoCo 1 and 2 models were also available on the CoCo3, e.g. RS-232 serial, cassette, right and left joystick and a 40-pin expansion slot.)
The built-in Language, named Disk Extended Color Basic 2.1, was a Microsoft BASIC with enhancements by Microware. It was similar to that of the CoCo2, but Microware added the commands/functions to take advantage of the higher resolution graphics and text.
The CoCo3 was upgradeable to 512 KB RAM. (After-market RAM upgrades have gone as high as 8MB, with rumors that 16MB and 32MB RAM upgrades may also be possible). A Multi-Pak (a 4-port bus expander) plugged into the Expansion Slot allowed use of controllers for floppy disk drives, hard drives (MFM, RLL, SCSI and now even IDE), multi-port true RS-232 devices, MIDI units and much much more.
As its microprocessor was still an 8 bit (strange choice when Atari and Commodore were using a 68000), it couldn't access simultaneously to the 128k (or 512k), and thus used several RAM banks which could be switched (as the Thomson TO8, or MSX 2 computers).
Unlike the CoCo and CoCo II the 3 had an interrupt controller. This did away with a lot of the timing loops used in its predecessors, and actually took some of the fun out of programming in Machine Language.
Tandy made several prototypes of a Color Computer model IV but it was never released.
Contributors: D. Francis
Color Computer 3
Tandy Radio Shack
END OF PRODUCTION
BUILT IN LANGUAGE
Disk Extended Color Basic 2.1 (Microsoft BASIC, with enhancements by Microware)
Motorola 68b09e (uses an external clock generator)
1.79 MHz (0.89mhz under RS-DOS for compatability with FD expansion unit)
128 KB (up to 512 KB. There were 1MB and 2MB upgrade boards as well)
32x16, 40x25, 80x25
Several graphic modes, the most interesting were: 320x200 (16 col.), 640x200 (4 col.), 640x400 (4 col. if 512 KB RAM)
See comment below
SIZE / WEIGHT
Tape, Composite Video, analog RGB connector for use with Tandy CM-8 monitor, 2 joystick ports, cartridge slot, RS232
with optional disk drive : RS-DOS, OS-9 Level 2 was also popular