Color Computer 1
The 6809E with a 6847 VDG, 6883 SAM and two 6821 PIAs.
Open the Color Computer 1 in Retro Bench- Also
- CoCo 1
- Year
- 1980
- CPU
- 6809E @ 0.89 MHz
- RAM
- 4 to 64 KB (4116 DRAM)
- ROM
- Color BASIC mask ROM, 8 KB
- Video
- MC6847 VDG: 32 × 16 text, PMODE hi-res, 9 colors
- Sound
- 6-bit DAC and single-bit sound via the $FF20 PIA (U4)
- OS
- Color BASIC (E and D layers add Extended and Disk)
Chips
| Chip | Where | Role |
|---|---|---|
| MC6809E microprocessor | Main CPU, 8-bit with 16-bit registers. Same CPU in every CoCo and in the Dragon 32 and 64. | |
| MC6847 video display generator | Text, semigraphics and color video from screen RAM. Used in the CoCo 1 and 2, the MC-10 and the Dragon 32 and 64. | |
| MC6883 synchronous address multiplexer | Makes all clocks from the 14.31818 MHz crystal, the DRAM strobes and address multiplex, and the device selects. Used in the CoCo 1 and 2 and the Dragon 32 and 64. | |
| MC6821 peripheral interface adapter | U8 ($FF00, keyboard) / U4 ($FF20, sound, cassette, RS-232) | Two 8-bit parallel ports with handshake lines. |
| 4116 DRAM 16K x 1 | U20-U27 | Dynamic RAM, 16K x 1 (lower 16K on the Spectrum) |
| Color BASIC mask ROM | Color BASIC ROM, 8 KB on the CoCo 1, 16 KB total on the CoCo 2 per the sheet. | |
| MC14529B dual 4-channel analog data selector | U9 | Joystick axis select for the A-to-D comparator, and sound source select for the TV and monitor. |
Ports and connectors
- Cartridge slot (Program Pak), 40-pin card-edge socket UNVERIFIED
- Joystick ports (right P3, left P4), DIN socket, 5 pins used (6-pin shell)
- Cassette (P5), 5-pin DIN socket (180°)
- Serial I/O (P2), 4-pin DIN socket
- RF out, Phono (RCA) jack UNVERIFIED
- Transformer board to main board (E1 to E4), Four spade lugs from the transformer assembly
Power rails
| Rail | Expect | Measure at |
|---|---|---|
| +5 V | +5 V | 6809E pin 7; SAM pin 40; TP12 |
| +12 V | About +12 V | TP9; 4116 pin 8; coco-cart pin 2 (cartridge) |
| -12 V | About -12 V | TP10; coco-cart pin 1 (cartridge) |
| -5 V | About -5 V | TP11; 4116 pin 1 |
Symptoms
- No boot: check 6809E, SAM, Color BASIC ROM
- No or bad video: check VDG, SAM
- Dead keys: check 6821 PIA
- No sound or tape: check 6821 PIA
- RAM errors or wrong memory size: check 4116