To make a long story short. After swapping my 89 watt opteron 148
(single core 2200mhz) for a 110 watt opteron 180 (duel core 2400mhz)
my computer no longer responds to the start button on my case. The
system started normally after the BIOS updates needed for dual core
support on my socket 939 Biostar Tforce 4U (NVIDIA nForce4 Ultra
chipset). The only change I made was the new CPU, and when I went to
start my computer the power button did not work. After 5 minutes of
pushing the power & reset buttons I was about to give up when it
suddenly came on. Runs fine and stable once started and even
overclocks stable to at least 2800mhz at stock voltage. Once started I
can restart and go into the BIOS and change the settings to restart on
power failure. Now I start my computer by turning the power supply on
& off until my machine fires up.
I just replaced my old 500 watt power supply with a new 500 watt
supply today thinking that might be it.
Any suggestions would be welcome.

System specs
socket 939 Biostar Tforce 4U (NVIDIA nForce4 Ultra chipset) mainboard.
Opteron 180
1 gig Mushkin PC4400 ram (2 x 512)
2 DVD burners
2 HDD's
floppy
NVIDIA 6800gs PCIe video card
High def TV card

My old opteron had been running fine at 2750mhz (10 x 275) for over
two years in this system.