Athlon 64 Memory: Rewriting the Rules
 

One of the more vexing discoveries as memory performance testing was extended to the Athlon 64 platform was that memory often did not perform the same on both platforms. You simply could not assume that a memory that did DDR550 on the Intel 478 chipset would perform the same on the Athlon 64. We have also discovered that certain memory actually performs much poorer on Athlon 64 than on Intel 478, while other memory consistently performs much better on Athlon 64. With these variations, it was time to establish an Athlon 64 memory test platform and run new baseline tests on some of the best recent memories

http://anandtech.com/memory/showdoc.aspx?i=2226&p=1

"We have found the fastest performance on AMD Athlon 64 chipsets (nForce3, VIA K8T800 PRO) to be achieved at Cycle Time or tRAS of 10. Athlon 64 platform benchmarks were, therefore, run with the tRAS timing of 10 for all A64 benchmarks."

have not heard of this yet; it wasn't the case on the previous nForce3 chip
http://www.madshrimps.be/?action=get...&articID=16 7

Memory that does good with all my P4, performs poorly even with AXP.:)