tim: vet du hur det ligger till med 667 MHz-minnen och MP (2008)?
OK har kollat runt å fan ett svar till dig!
667Mhz vs 800MHz FB-DIMMs in the 2008 Mac Pro
ANALYSIS
If you have a big investment in 667MHz memory, you can use those FB-DIMMs with the new Mac Pro. The tests we ran show a maximum penalty of 4% in speed. Considering the advantage over the 3.0GHz 8-core "Cloverfield" Mac Pro ranges from 18% to 24% when running Photoshop, After Effects, and Aperture, you might feel you can live with a 4% hit.
But if you want to squeeze every ounce of speed out of your new Mac Pro, then you'll want 800MHz FB-DIMMs -- eight sticks preferred.
FUTURE PROOFING
If you own a 2006/2007 Mac Pro that takes 667MHz FB-DIMMs and you are planning a memory purchase, you might consider buying 800MHz FB-DIMMs. They work fine, though they will run at 667MHz. Yet if you are planning to buy a 2008 Mac Pro in the near future, going with 800MHz FB-DIMMs will "future proof" your memory investment.