We all hate that adding DDR3 sticks to a server slows down the QPI speed (or RAM Bus for lack of a better example).
That changes with the Nehalem EX proc (and perhaps Westmere), as the CPU governs the speed. You can throw up to 16 sticks of DDR3 RAM per CPU at either 800, 978, or 1066MHz, and the governing factor is the CPU:
|Model||Speed||TDP Power||Cache||Cores||QPI Speed|
6.4GT/s – 1066MHz
5.86GT/s – 978MHz
4.8GT/s – 800MHz
As long as you stay with the 6.4GT/s CPU, you’ll be running at 1066MHz!