John R Pierce spake the following on 3/22/2007 11:02 AM:
I seem to recall there were some generations of Opterons where if you ran 3 or fewer banks (6 or fewer dimms, balanced for dual channel), you could run at PC3200 speed, but if you populated all 4 banks (8 dimms), you had to downgrade the memory bus to PC2700 or something. Could be you're running into something like this.
Also check the voltage req. of the memory. Maybe the board is under volt for the specific ram.