MSX2 (generic)
The V9938 and a battery-backed clock on the MSX1 standard; one-chip MSX-Engines on most boards.
Open the MSX2 (generic) in Retro Bench- Also
- Any MSX2 machine (Sony HB-F, Philips NMS / VG-8235, Panasonic FS-A1, Yamaha YIS and others)
- Year
- 1985
- CPU
- Z80A @ 3.579545 MHz (clock from the V9938 CPUCLK pin)
- RAM
- 64 KB minimum; many have 128 KB or more behind a memory mapper (I/O $FC-$FF)
- ROM
- 48 KB: 32 KB MSX-BASIC 2.0 main ROM + 16 KB sub-ROM (often plus a disk ROM)
- Video
- Yamaha V9938 with 64 or 128 KB VRAM: up to 512 x 212 (424 interlaced), 512-color palette, 256 colors in SCREEN 8
- Sound
- AY-3-8910 / YM2149 PSG (often inside an MSX-Engine)
- OS
- MSX-BASIC 2.0; MSX-DOS with a disk drive
Chips
| Chip | Where | Role |
|---|---|---|
| Yamaha V9938 MSX-Video display processor | Varies by maker; 64-pin shrink DIP (SDIP, 1.778 mm pitch), usually beside the VRAM | MSX2 video: TMS9918A-compatible VDP with bitmap modes, 512-color palette, RGB and composite out, 64-128 KB VRAM |
| Z80A CPU | Varies by maker; Z80A or compatible, clocked from V9938 pin 8 | Main CPU (8-bit, 40-DIP) |
| AY-3-8910 programmable sound generator (40-pin) | Discrete AY-3-8910 / YM2149 on early MSX2; inside the S3527 or S1985 MSX-Engine on most | Three tone voices, noise and envelope, plus two 8-bit I/O ports (the MSX joystick ports and the cassette input) |
| 8255A-5 programmable peripheral interface | Discrete 8255 on early MSX2; inside the S3527 or S1985 on most | Three 8-bit programmable I/O ports (A, B, C). |
| Yamaha S1985 MSX-System II (MSX-Engine) | Boards that use it in place of the discrete 8255 and AY-3-8910 | One-chip MSX2 I/O: S3527 functions plus memory mapper, RP5C01-compatible clock and backup RAM |
| Yamaha S3527 MSX-System (MSX-Engine) | Boards that use it in place of the discrete 8255 and AY-3-8910 | One-chip MSX I/O: YM2149-compatible PSG, 8255-compatible PPI, slot and memory control, printer interface |
Ports and connectors
- Cartridge slot, 50-way 2.54 mm card-edge socket (25 + 25), odd pins one side, even the other UNVERIFIED
- General-purpose I/O port 1 (joystick 1), DE-9 male on the computer ("9-pin AMP compatible")
- General-purpose I/O port 2 (joystick 2), DE-9 male on the computer ("9-pin AMP compatible")
- Cassette interface, 8-pin DIN 270 degrees (DIN 45326)
- Printer port, 14-pin Amphenol (Centronics-style ribbon) connector
- Video / audio DIN (where fitted), 5-pin DIN 180 degrees
- Composite video (RCA, where fitted), RCA (phono) jack
- RF out (to the TV aerial input), RCA (phono) jack
- Audio out (RCA, where fitted), RCA (phono) jack
Power rails
| Rail | Expect | Measure at |
|---|---|---|
| +5 V | 4.75-5.25 V | Z80A pin 11; V9938 pin 58; msx2-cart pins 45, 47 (cartridge) |
| +12 V | +12 V | Cartridge slot pin 48 |
| -12 V | -12 V | Cartridge slot pin 50 |
| GND | 0 V | Z80A pin 29; V9938 pin 1; V9938 pin 20; msx2-cart pins 41, 43 (cartridge) |
Symptoms
- Power LED on, black screen, no boot: check V9938, Z80A, S1985, S3527
- Boots, but garbage or wrong colors, especially in SCREEN 5-8: check V9938
- Clock and SET settings lost at every power-on: check S1985
- No sound, joysticks dead, dead keyboard rows: check S3527, S1985, AY-3-8910, 8255A
- Hum bars, resets on load