Trouble booting a SMP kernel

I need a little help diagnosing a problem booting a 5.1-RELEASE SMP kernel.

The GENERIC kernel boots just fine. When I boot a GENERIC kernel with SMP
enabled the boot fails early in the boot process.  The text from the 
console is below:

Programming 16 pins in IOAPIC #0
IOAPIC #0 intpin 2 -> irq 0
Programming 16 pins in IOAPIC #1
AP #1 (PHY #1) failed!
panic y/n? [y] n
<snip>
APIC_IO: Testing 8254 interrupt delivery
[system is locks up at this point, no more messages]

Also fails to boot a FreeBSD 4.4 SMP kernel, which leads me to beleive 
it's a hardware
problem.

Is this indicative of a failed processor or is it the motherboard?

Hardware is a Tyan Thunder LE-T, BIOS v1.06, Dual Pentium III 1133 MHz, 
2GB RAM.

Any advise on diagnosing the problem is greatly appreciated.

-- Scott