Oric Atmos
The Oric-1 board in a red-and-black case with a full-travel keyboard, a FUNCT key and the V1.1 ROM fixes.
Open the Oric Atmos in Retro Bench- Also
- Oric Atmos 48K (16K model also listed)
- Year
- 1984
- CPU
- 6502A @ 1 MHz
- RAM
- 48 KB (eight 4164) or 16 KB
- ROM
- 16 KB Oric Extended BASIC V1.1
- Video
- HCS10017 ULA, same modes as the Oric-1; RGB and PAL UHF
- Sound
- AY-3-8912, 3 voices + noise, internal speaker
- OS
- Oric Extended BASIC V1.1
Chips
| Chip | Where | Role |
|---|---|---|
| Oric ULA HCS10017 | IC7 (same numbering per the Oric/Atmos checklist; verify) | Clock divider (12 MHz to 1 MHz), address decode (ROM, page-3 I/O, RAM), DRAM multiplexing and refresh, video generation (RGB, sync) |
| 6502 / 65C02 CPU | 6502A (Atmos schematic not seen) | CPU |
| 6522 VIA | IC6 (same numbering per the Oric/Atmos checklist; verify) | Two 8-bit ports, timers, serial and user port |
| AY-3-8912 sound chip | IC4 (verify) | Three-voice programmable sound generator with one 8-bit I/O port |
| 23128 Mask ROM 16K×8 | IC9 (verify) | BASIC and KERNAL ROMs (C16, Plus/4, C64C short board, C128) |
| 4164 DRAM 64K×1 | IC12-IC19 (verify) | Main RAM (8 chips = 64 KB) |
Ports and connectors
- Expansion port (rear), 34-way right-angle IDC pin header PL2 (2 x 17), odd/even numbering
- Printer port (rear), 20-way right-angle IDC pin header PL1 (2 x 10), Centronics-style parallel, odd/even numbering
- RGB monitor socket, 5-pin DIN 180 degrees
- Cassette and sound socket, 7-pin DIN 270 degrees
- 9 V DC power socket, DC jack, center positive (SK3)
- TV (RF) output, Phono socket from the UHF modulator
- Keyboard connector (internal, PL3), 14-way keyboard ribbon connector UNVERIFIED
Power rails
| Rail | Expect | Measure at |
|---|---|---|
| +5 V | 4.95-5.05 V | 6502 pin 8; ULA pin 24; VIA pin 20; AY-3-8912 pin 3; 4164 pin 8; 23128 pin 28 |
| 0 V (regulated by the 7905) | 0 V reference | 6502 pin 1; 6502 pin 21; ULA pin 6; VIA pin 1; AY-3-8912 pin 6; 4164 pin 16 |
Symptoms
- Dead: no picture, nothing happens: check ULA, 6502, 23128
- Random white blocks that never clear, no sign-on: check 4164, ULA, 23128
- Cursor stuck bottom right with thin vertical lines: check VIA
- Works, then stops after about five minutes
- +5 V missing or low: check 4164, 6502, VIA, AY-3-8912
- No sound (keyboard click missing too): check AY-3-8912, VIA
- Picture on the TV but not on the RGB monitor (or the reverse): check ULA
- TV colors wrong, yellow looks white, shimmer
- Tape will not load: check VIA
- Recorder motor does not start or stop: check VIA
- Keys dead or double, one row or column out: check AY-3-8912, VIA
- Will not boot after a CPU change: check 6502