The Tandy TRS-80 Color Computer is an affordable personal machine. This machine was designed to compete with the Commodore VIC-20. MSRP is $399.

  • Model 26-3001
  • MC6809E  0.895 MHz
  • MC6883/SN74LS783/SN74LS785 Synchronous Address Multiplexor
  • MC6821 or MC6822 chips
  • 4KB RAM
  • MC6847 MDA
  • Cartridge slot

The Synchronous Address Multiplexor is a multifunction device that performs the following functions:

  • Clock generation and synchronization for the 6809E MPU and 6847 VDG
  • Up to 64K Dynamic Random Access Memory (DRAM) control and refresh
  • Device selection based on MPU memory address to determine if the MPU access is to DRAM, ROM, PIA, etc.
  • Duplication of the VDG address counter to “feed” the VDG the data it is expecting

The TRS-80 Color Computer BASIC is licensed from Microsoft which allows for excellent compactivity with business software. The cartridge slot is fully addressable so there is no issue with expansions.

The CPU in the TRS-80 Color Computer is far easier to work with compared to the 6502. The 6809 has a 16-bit primary accumulator, 2 index registers and 2 stacks which can support a staggering range of programming techniques. The 6809 runs at 0.895 MHz but it can be switched to 1.79 MHz in software.

In alphanumeric mode, each character is a 5 dot wide by 7 dot high character in a box 8 dots wide and 12 lines high. This display mode occupies 512 bytes of memory from $400-$5FF and is a 32 character wide screen with 16 lines. The ROM character generator only holds 64 characters, so no lowercase characters are provided. “Lowercase” characters are rendered as uppercase with inverted color. On most CoCo generations it is green on very dark green.

The system board is fairly well made and it has relatively strong design and manufacturing.

The keyboard is fairly well made and it can be used for working in BASIC or another program.