src/devices/bus/pc8801/README.md
MIDI interface
"Sound Board", single YM2203C OPN, single joy port, mono out
Modem board, full duplex 300bps
Parallel I/F board
extra μPD8086 CPU + 8253, 8255 and 8259 i/f, able to run MS-DOS 1.25, requires extra ROMs for both sides
VTR capture card "Video art board" / "Video digitizing unit", 16-bit color
CMT i/f board
"Multi board B", upgrades a FH to MH and FA to MA (?)
"Sound Board 2", single YM2608 OPNA, single joy port, stereo out. -24 is the internal FH / MH version, -25 is the internal FE / FE2 with YM2608B. Standard and on main board instead for FA / MA and onward;
-31 is CD-ROM SCSI i/f (built-in for MC, optional for MA+), -30 is virtually same to PC Engine CD-ROM² drive
Network board mapping at $a0-$a3
PCG and 3x DAC_1BIT at I/O $01, $02. PIT at $0c-$0f
2x PSG at I/O $a0-$a3, mono out. Has goofy extra connector on top and a couple jumpers, guess it may cascade with another board for 2x extra PSGs at $a4-$a7
YM2151 OPM + YM3802-X MIDI controller, stereo out, has own internal XTAL @ 4MHz. Has an undumped PAL/PROM labeled "HAL-881"
earlier version of HIBIKI-8800 board with no MIDI? cfr. GH #10703
"Sound Board X", 2x OPM + 1x SSG. Used by NRTDRV88J, more info at GH #8709