Well I have started fiddling with a PC/Server 500 with P390 mainframe card. It came with a duff VGA card which I replaced and then the fun started. It reports duff RAID config and won't boot. It also refused to read any floppy disks so I couldn't even start to debug.
Sadly it has a "Media Sense" floppy disk drive so I couldn't try another drive. Fortunately a cleaning disk from E-Bay that arrived yesterday seems to have restored some functionality and I can read many disks, but its still not perfect.
I will try and take some pictures and post later...