This is really weird. Maybe you have some insight on this phenomenon:

I am now working on my UMC 481/482 board. This motherboard has the hardware flush circuit (for L1 cache) built into the motherboard. I am using MR BIOS on this motherboard, which doesn't know what hardware is on this particular motherboard for cache invalidation. So MR BIOS enable the BARB input method via software, which is not needed, so I normally disable the BARB with cyrix.exe -b- The board works fine with the SXL and Adaptec 1520B.

The strange thing is when I use the 1540C. The board hangs at boot, right after cyrix -b- is initiated from autoexec.bat. If I remark out cyrix -b- (REM cyrix -b-), the board works fine in DOS and Windows with the SCSI DMA 1540C controller. What is going on here?