MSX, PC-8801 and Sharp X1
These machines use the Z80 (CPU families). The MSX maps memory through slots and subslots. Its MegaROM cartridges switch banks with a mapper. The PC-8801 and the X1 were two of Japan's four major home computers, with the FM-7 and the MSX.
MSX, MSX2, MSX2+ and turbo R
Hardware
| Fact | Value |
|---|---|
| Years | Announced by ASCII on 16 June 1983; first machine on sale 21 October 1983; MSX2 in 1985; MSX2+ in 1988 (Japan only); to 1990 |
| CPU | Z80A at 3.58 MHz; R800 on the turbo R |
| RAM | 8–64 KB; 64–512 KB on MSX2; up to 4 MB per slot through a memory mapper |
| Video | TMS9918 family, V9938, V9958; European machines use the TMS9929A (not confirmed) |
| Sound | AY-3-8910 or YM2149; Konami's SCC chip inside some cartridges adds five channels |
Sources: Wikipedia: MSX, MSX Wiki.
Slots. Slots and subslots are selected through the PPI at port A8h and the register at FFFFh. VRAM is reached only through VDP ports 98h and 99h (not confirmed) (MSX Wiki: Slots).
How games were made and loaded
Cartridges were common on the MSX. MegaROM cartridges use bank-switching mappers: Konami, Konami SCC, ASCII 8K and ASCII 16K. An emulator needs the right mapper type to run a dump (not confirmed) (MSX Wiki: MegaROM mappers).
Media and image formats
Images are ROM dumps with a mapper type, DSK disks and CAS tapes (not confirmed) (openMSX manual).
Tools
- openMSX has a Tcl console and a separate debugger (openmsx.org). An agent can drive captures through the Tcl console with a script (re-observe).
- Ghidra has the Z80 built in. Unicorn has no Z80. For ground truth use a small core such as iz80 (CPU families).
The MSX Resource Center is at msx.org.
Projects to learn from
None listed yet.
For an exact reimplementation
- Record the mapper type of the cartridge. Name functions by bank and address.
- Record the slot layout of the reference machine.
- Record which VDP the reference machine has. European machines use the TMS9929A.
NEC PC-8801
Hardware
| Fact | Value |
|---|---|
| Launch | November 1981 |
| CPU | Z80 |
| Sound | YM2203 from the mkII SR, later YM2608 |
Its disk unit has a second Z80 (not confirmed). Source: Wikipedia: PC-8800 series.
How games were made and loaded
The PC-8801 ran N88-BASIC. Ys, Thexder, Snatcher and the Dragon Slayer series first appeared on it (Wikipedia: PC-8800 series).
Media and image formats
D88 is the usual disk image (not confirmed).
Tools
MAME covers the PC-8801, with a shared debugger and Lua scripting (MAME debugger). Ghidra has the Z80 built in.
Projects to learn from
None listed yet.
For an exact reimplementation
- The disk unit's second Z80 runs its own code (not confirmed). Treat it as a separate program.
- Record the sound chip of the reference model.
Sharp X1
Hardware
| Fact | Value |
|---|---|
| Years | 1982; X1 turbo in 1984 (not confirmed) |
| CPU | Z80A at 4 MHz (not confirmed) |
| Video | HD46505 CRTC, PCG (not confirmed) |
| Sound | AY-3-8910 (not confirmed) |
Source: Wikipedia: Sharp X1.
How games were made and loaded
None listed yet.
Media and image formats
None listed yet.
Tools
MAME covers the X1, with a shared debugger and Lua scripting (MAME debugger). Ghidra has the Z80 built in.
Projects to learn from
None listed yet.
For an exact reimplementation
- Confirm the CPU clock and the chips from a second source before you model timing.