TRS-80 CoCo

The Tandy TRS-80 Color Computer, affectionatly nicknamed CoCo, was a home computer launched in 1980. It had limited video and sound capabilites compared to its rivals, but was easy to program for and was produced in various incarnations until 1991.


The follow-up to the TRS-80, the CoCo is actually incompatible with its precursor's hardware due to a completely different processor (Motorola 6809E vs. the Zilog Z80). This processor was actually more powerful than that used in many machines, which led to a higher price-tag and a correspondingly smaller user base.

The CoCo went through three revisions, taking it from the start of the 1980s through to the start of the 1990s. Impressively, each version had a high level of backwards compatibility with the software of previous revisions.

The CoCo line ultimately succumbed to the rise of the IBM PC Clone.

Technical Specifications

The CoCo 1 and 2 are largely identical under the hood, consisting of five LSI chips:

  • MPU: An MC6809E Microprocessor Unit that acted as the machine's brain.
  • SAM: A MC6883/SN74LS783/SN74LS785 Synchronous Address Multiplexor that controls the DRAM, clock synchronization and a bunch of other tiny little things.
  • VDG: A MC6847 Video Display Generator, capable of drawing graphics in up to nine colours to a 256x192 resolution display, supporting 16 lines of 32 characters on screen at once.
  • PIA: Two Peripheral Interface Adapters, either MC6821 or MC6822 chips, handing I/O operations for cassete decks, the keyboard, and other things that plug into the machine.

The CoCo 3 made a few more significant changes:

  • ACVC: A new ASIC-manufactured VLSI, dubbed the Advanced Color Video Chip, that integrated the capabilities of SAM AND VDG while enhancing their capabilities (for example, adding support for lower-case characters and 40-80 character displays).
  • MPU: Bumped up to a MC68B09E.
  • PIA: Bumped up to MC68B21s.

TRS-80 CoCo games