Why does an Athlon MP system with a Tyan S2466 motherboard hang at boot during Adaptec init for the SMP kernel, but works with uniprocessor kernel?

Version: Red Hat Enterprise Linux, GRUB bootloader

Symptoms:

System: Athlon MP Tyan S2466 motherboard, dual MP1800+ chips, 1GB RAM, Adaptec 78xx U160 SCSI. System hangs at boot during Adaptec init for the SMP kernel, but works with uniprocessor kernel.

Symptons are random hangs during the boot process, sometimes while starting xinetd, sometimes when starti...