I will try to keep this as short and succint as possible.
I upgraded my Phenom and MSI mobo to a Gigabyte 990XA-UD3 & FX-6200 Bulldozer.
All worked relatively okay. It would crash after around 2-3 hours use, consistently. Temps were not too high, but very very strange, they were fluctuating around 7-8 degrees a second, never going above 35 or below 25 celsius, but every second it would drop or incresase by around 7 degrees and the fan would spin much faster/slower in parallel with this.
I updated BIOS using @BIOS (Which I know learn doesn't work) which gave me many issues. I managed to load the original F2 BIOS back on via usb, however that left me in a state where my PC would turn on (lights/fans on) but nothing more, nothing on display or anything. Using my old Phenom I managed to update the BIOS to the latest (F12), where it would now boot with my bulldozer.
When I say boot, it was not recognising my HDD. It is recognised in BIOS and in command prompt, but it is not deteced via the windows installer. After many attempts to resolve this the one that worked was the cleanall function in command prompt.
SInce it has been detected I have installed and reinstalled Windows about 3-4 times (setting the drive as AHCI, IDE, using optimisid defaults etc) but it now has this issue where it either hangs at 'starting windows', it hangs for a second at 'starting windows' and then BSOD's and reboots, or (when i try to boot into safe mode) it stops at the CLASSPNP.sys driver and then BSOD's and reboots.
As I have said my BOIS is fully up to date and functional, and I have tried all the different settings, in particular AHCI/IDE and the optimised and fail safe defaults. I have also ensured all unecessary USB drivers or accessories are disconnected on boot/windows install.
After you update your BIOS you should always clear the CMOS memory. It sounds as if you are having memory problems with the new BIOS if you are still having problems after clearing the CMOS then try and enter the memory timings manually.