reinstall the bios
I tried both downgrading and reinstalling the bios. Downgrading fails during the 3rd or 4th step, something about flashing the desktop management portion. iflash2 will not let me flash the same version it says bios IDs already match. How can i force it?
does it fail to downgrade with both cpus?
Yes, it failed to downgrade with both CPUs. I just swaped in a Q8200 from another PC and it works fine, put the Q8300 in the PC it came from (non-intel mobo) and it's happy also. Very odd. I was able to re-flash the current BIOS using the windows utlity instead of iflash (downgrade does not work in windows or iflash).
Same problem here:
DG33FB with Q8400 fail reboot and hangs on a black screen.
Shutdown works correctly.
Cpu not correctly detected (due to old microcode)
With old cpu there are no problems at all, so it is not a problem of bios corruption.