Made some progress on the Omron Luna 88K² workstation; now it passes most of its firmware diagnostics and boots to the monitor. The keyboard is a high-level emulation with some unsatisfying gaps in the key mapping (even finding a good picture of the key tops and positions has been a challenge), but it's usable for now.
The "xp" is a HD647180X0FS6 I/O processor that drives two serial ports, a printer port, and possibly is involved with the optional floppy disk card. While the firmware for this chip hasn't been dumped yet, it might not be required as the host uploads code dynamically and it should be possible to get it working once some missing features of the CPU are emulated.
The other major outstanding area of work is the MB89352A SCSI controller; once this is up and running the next major milestone will be booting UniOS.
How accurate are the current GEW8 envelope rates meant to be, if you happen to know? (I know they're based on the values from the OPL4 manual)
I think the reason that string part is missing from the demo is just because the attack on "Strings 2" is way slower than it's supposed to be and the notes end up being too short to be audible. I'm currently fudging the GEW7 envelopes a bit for a similar reason, but I wonder if the envelope rates on both chips are actually supposed to be the same (or at least closer to each other).
GEW8 envelopes are, as you noticed, taken from OPL4 and fudged a little to make the Sega games sound good. But Sega largely used the chip as a dumb sample player with some occasional LFO so those games were far from a good test suite.
With sprites re-enabled and an additional mode bit identified - bit 12 of the matrix-vector multiply command header turns it from "Matrix * Vector + Vector" into "Matrix * Vector - Vector" - Final Furlong actually starts to look like a game.
Added support for the CuRAM-16 XMS card to the PS/2. The Model 80 isn't fully compatible with it but the IBM first-party RAM expansion cards have option ROMs and no documentation. This is enough to install and run Doom (...on a 16MHz 386.).
I have a bunch of cards emulated now. The Sound Blaster MCV's FM audio works but digital audio crashes the emulated system.
Also working on the M-ACPA DSP card. I don't have any of the analog section hooked up yet but the DSP communication works.