Japanese 16-bit and 32-bit computers
The X68000 uses the big-endian 68000 line. The PC-9801 and the FM Towns use x86 (CPU families). Each machine has its own custom video and sound chips. The PC-98's chips differ from the IBM PC's, even though the CPU and the OS match. A game that uses Human68k or MS-DOS can be traced at its OS calls. A game that drives the chips must be traced at its hardware register writes.
Sharp X68000
Hardware
| Fact | Value |
|---|---|
| Years | Released in March 1987, in Japan only; to 1993 |
| CPU | HD68HC000 at 10 MHz; 16 MHz on the XVI; 68EC030 at 25 MHz on the X68030 |
| RAM | 1–4 MB, to 12 MB |
| VRAM | 1056 KB, split into graphics, text and sprite areas |
| Sprites | 128, 32 per line; raster interrupts can raise that to 512 |
| Sound | YM2151 with eight FM channels; MSM6258 ADPCM channel at 15.6 kHz |
Source: Wikipedia: X68000.
How games were made and loaded
The OS is Human68k, an MS-DOS-like OS made by Hudson Soft. Floppies hold 77 tracks of 8 sectors of 1024 bytes at 360 rpm, 1232 KiB in all (Wikipedia: X68000).
Media and image formats
The XDF, DIM and HDM image formats still need sources.
Tools
- Use MAME's debugger when no other debugger is available.
- The XM6, PX68k and Unz debuggers still need sources.
- Ghidra has the 68000 built in. Unicorn runs 68000 code but none of the X68000's chips.
Projects to learn from
None listed yet.
For an exact reimplementation
- Record whether the game uses raster interrupts to show more than 128 sprites.
- Record the model. The XVI and X68030 run faster.
NEC PC-9801
Hardware
| Fact | Value |
|---|---|
| Years | Launched in October 1982; the line ended on 30 September 2003 |
| Sales | 18.3 million units |
| CPU | 8086 at 5 MHz; later V30, 80286, 80386 |
| RAM | 128 KB to 640 KB at first |
| Video | Two μPD7220 controllers, for text and graphics separately; 640x400 in 8 colours, later 16 from 4,096 |
| Blitters | GRCG (1985) and EGC (1986) |
| Sound | FM on the PC-9801-26 card (YM2203) and the PC-9801-86 card (YM2608) |
Source: Wikipedia: PC-98.
How games were made and loaded
The PC-98 runs x86 code under MS-DOS and N88-BASIC(86). Its display and sound hardware differ from the IBM PC's.
Media and image formats
| Kind | Formats |
|---|---|
| Floppy | FDI, FDD, D88/D98, HDM, NFD |
| Hard disk | HDI, NHD |
Sources: libretro: Neko Project II Kai, Batocera wiki.
Tools
- Neko Project II Kai emulates the PC-98. It needs BIOS, font and sound ROMs.
- GameFrame's DOS tools help with the CPU and DOS layer (DOS games). The hardware layer needs its own notes.
- Ghidra has x86 real mode built in. Unicorn runs x86 16-bit code (re-emulate).
Projects to learn from
None listed yet.
For an exact reimplementation
- Use the DOS method for the program and its calls (DOS games).
- Write separate notes for the μPD7220, GRCG and EGC. The IBM PC's VGA notes do not apply (2D graphics).
- Record which FM sound card the reference recording used.
Fujitsu FM Towns
Hardware
| Fact | Value |
|---|---|
| Years | Released on 28 February 1989; to 1997 |
| Sales | About 500,000 |
| CPU | 80386DX at 16 MHz |
| Sound | RF5c68 PCM, YM2612 FM |
| Sprites | 1024 |
| Media | CD-ROM drive as standard |
Source: Wikipedia: FM Towns.
The FM Towns Marty console (1993) runs Towns games.
How games were made and loaded
Towns OS is MS-DOS with the Phar Lap DOS extender (Wikipedia: FM Towns).
Media and image formats
Games came on CD-ROM. No image format details are listed yet.
Tools
- A game built on the Phar Lap extender needs a loader for extended DOS programs. That differs from a real-mode MZ load (DOS games).
- Ghidra has 32-bit x86 built in. Unicorn runs 32-bit x86 code.
Projects to learn from
None listed yet.
For an exact reimplementation
- Identify the extender and its executable format before loading the program into Ghidra (IBM PC).
- Write separate notes for the FM Towns sprite and sound hardware.