Why original IBM BIOS was requried for Xenix?!

The Roms it came with did not work, also the disks had to have perfect media. Everything bad to be formatted beforehand. So, I got IBM ROMS and it worked, then got some other roms so the keyboard speed switch would work, while the IBM ROMS were installed there was a simple program that would kick up the speed, and turn wait states off. It was slightly faster than a 6mhz AT for DOS and we did not have Xenix 286. Got me through K&R and passed the class, but do useful work? No.

We found out after the third try, that both the IBM and one of the clone BIOSes would run the install, and all of them would boot. ( And an OMTI Rll controller, supported... Dual hard disks too. ) I needed an assembly language program to much the speed up to 10mhz, and it still ran fine, right up to the 'make nethack' then 4 hours later...beeeep beeeep beep. OS not found. We never figured out weather it was a out of memory error or a temp file error ... But the OS was gone.