Have a 4100 here, still OS 3.x
Machine went down with flickering system-LED, called Adaptec. Machine has no warranty left, so they told me, they won't repair.
Nice way of doing business, but that underlines what I think of this company for several years now - /dev/null is the best place for them. Support told me too, that the drives have XFS - but I was unable to mount them on Linux, FreeBSD or NetBSD - will try further, perhaps they use a rare partition-scheme. I doubt, that the machine has a "normal" BIOS, I suggest them to have something like OpenFirmware or simular.
I removed all drives (4x40) and machine came up again, now I try with 4x120 WD - new RAID5 with one spare is resyncing atm, guess that might take some hours.. ^^
I'm still interested in getting this machine to boot Linux or a more "normal" BSD like OpenBSD or NetBSD, but without more information it's hard to predict if we ever see a Snap booting a custom Linux. The machines has standard PC-hardware, so it should even boot with a vanilla 2.4.x or 2.6.x-kernel. Still the BIOS is a big "?"...
If I find the time, I will look into these .sup-files to get any information about the BIOS or the booting process, all we need is a bootloder..
I did not test 48bitLBA yet but I doubt Adaptec will ever provide a BIOS-update for the Promise-controllers.. :/