CPU failure???

We had a Sun 450 lock up yesterday morning. It was power cycled since it would not respond to ping, telnet or on the console. It came back up and everythind appeared normal, except when looking through the messages file it appears to only have 3 CPU's (there are 4) and I see the following error.

Jan 22 3:10:15 dfwnet2 unix: WARNING: status 'fail-Master Disable' for '/SUNW,UltraSPARC-II@0,0'

Are there any other possibilities besides a bad CPU?

TOPS-10 Symmetric Multiprocessing has good discussions on issues related to SMP hardware failures:

The Linux SMP FAQ is good too: