Andrew Lentvorski wrote:
The second part of the problem is that the trace length between the processor and the memory is somewhere in the range of 15-30cm. This is on the order of 1/2 to 1ns even at the speed of light (and the electrons do not move at that speed in copper). Even if you had a RAM latency of 0, sending the command and getting the response is limited to about 1ns in latency. That means that we have about a 2-3 to 1 CPU to memory mismatch that can never be fixed other than by parking memory right on the CPU.
The Opteron motherboards I have seen recently all seem to have the memory sitting right next to the cpu. I don't see how it could be 15-30cm to it. And the dual Opteron setups have dual memory banks, one right next to each cpu. This is one of the reasons why Opteron is my preferred cpu/mobo right now. That and the fact that you can cram at least 32G of RAM into these systems which makes them good for Xen.
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