Computer hangs AMD XD2100 SIS735 chipset

What would cause this system to hang up?

I just installed an EliteGroup K7S5A socket A motherboard with an SIS 735 chipset. On this board I installed a AMD XP2100 processor. And 512MB SDRAM. I flashed the BIOS to the latest Rev.

If I set the CPU PNP setting to 133/133, the appropriate setting for the 2100 chip, The computer will hang up. If I set to 100/133 the PC runs normally. The highest observed temp for the CPU has been 54C, I believe that is well with in the range for normal operations.