Atari 400
Membrane keyboard, one cartridge slot, the same chips as the 800.
Open the Atari 400 in Retro Bench- Also
- 400
- Year
- 1979
- CPU
- 6502B @ 1.79 MHz
- RAM
- 8-16 KB (4116 DRAM)
- ROM
- OS ROM 10 KB at $D800; BASIC on 8 KB cartridge
- Video
- ANTIC + CTIA/GTIA: 40x24 text, 320x192
- Sound
- POKEY, 4 voices
- OS
- Atari OS (400/800)
Chips
| Chip | Where | Role |
|---|---|---|
| 6502 / 65C02 CPU | A303 (CPU board) | CPU |
| ANTIC CO12296 / C021697 display processor | A302 (CPU board) | Display list processor: fetches screen data by DMA, halts the CPU, makes the NMI for VBlank and DLI, refreshes DRAM. |
| CTIA C012295 / GTIA C014805 | A301 (CPU board) | Color, luminance and sync out, player/missile graphics, triggers and console keys; divides the color clock for ANTIC. |
| POKEY C012294 | A101 (motherboard) | Four-voice sound, keyboard scan, eight pot (paddle) inputs and the SIO serial port. |
| 6520 PIA | A102 (motherboard) | Keyboard, cassette 1, IEEE-488 data (PET) |
| 4116 DRAM 16K x 1 | RAM board | Dynamic RAM, 16K x 1 (lower 16K on the Spectrum) |
| OS and floating point ROMs (400/800) | A103-A105 (motherboard) | Operating system (two 4 KB ROMs) and floating point package (2 KB ROM) on the 400/800. |
Ports and connectors
- SIO peripheral port (13-pin), 13-pin trapezoid, Atari proprietary
- Controller port 1 (DE-9), DE-9 male
- Controller port 2 (DE-9), DE-9 male
- Controller port 3 (DE-9), DE-9 male
- Controller port 4 (DE-9), DE-9 male
- Cartridge slot (30 contacts), Card edge 15/30, 0.1 in
- Power in (9 V AC), Two-contact round power jack (J204) UNVERIFIED
- RF out (TV), RCA phono jack
Power rails
| Rail | Expect | Measure at |
|---|---|---|
| +5 V A | +5 V | 7805 (A202) output; POKEY pin 17; ANTIC pin 21 |
| +5 V B | +5 V | Power supply board, after L201 |
| +12 V | +12 V | 78M12 (A201) output; RAM boards |
| -5 V | -5 V | Zener CR201 (5.1 V); RAM boards |
Symptoms
- Red screen: check 4116
- Dead machine, black screen: check 6502, ANTIC, GTIA
- No display, or blank or scrambled picture: check ANTIC, GTIA
- No color: check GTIA
- Dead keys: check POKEY
- Bad sound or SIO fails: check POKEY
- No joysticks, or no disk drive: check PIA
- Machine will not boot: check OS ROM
- Dead with the cartridge door open