Originally Posted by Quantum Reality

Um you should be able to run your RAM at 800. I've had a CPU like yours, a Q9550, and I had no issues running it at 800. The thing is, Intel CPUs prior to the i7 do not have integrated memory controllers and so the North Bridge has more flexibility in setting clock dividers that will let you run your RAM precisely as you wish it. For example a 4:5 divider would let your RAM run at basically DDR2-800 speeds.

This, however, is off topic since we're in an AMD forum. If you have questions about your Intel RAM speeds you should make a thread on the Intel Memory forum.