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?AM2 on single channel RAM?

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October 19, 2006 8:02:18 PM

We all know that AM2 adds little more than nothing to 939 regarding performance in dual channel mode, but what about single channel? Does for example a single channel 667MHz DDR2 remove the penalty of the single channel 400MHz DDR in the 939? Does it count anything when you're on onboard video, 667 vs 400MHz? Haven't found benchmarks about this so hope to find some experiences.

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October 19, 2006 8:05:41 PM

Quote:
We all know that AM2 adds little more than nothing to 939 regarding performance in dual channel mode, but what about single channel? Does for example a single channel 667MHz DDR2 remove the penalty of the single channel 400MHz DDR in the 939? Does it count anything when you're on onboard video, 667 vs 400MHz? Haven't found benchmarks about this so hope to find some experiences.


I think the performance is similar.
K8 works best with low-latency memory but not high-bandwidth memory.
October 19, 2006 10:17:09 PM

The K8 has excellent L1 cache hit rate, over 90%, an IMC which reduces RAM latency and low L2 capacity. The large L2 cache hides the latency, but it is not the case with K8 because of the IMC. It has sufficient memory bandwidth, but it starves for tighter RAM timings. The K8 with single DDR2-667 compared to single DDR-400 might be faster if realtime RAM latency is lower, or slower if the oposite is the case.
For example K8 on s939 with DDR-400 CL2 2-2-2 is same fast as K8 on sAM2 with DDR2-800 CL4 4-4-4. Althoguh the memory timings(in RAM cycles) of the DDR2 are double, the realtime latency in ns is equal. The freqfency of the DDR2-800 is twice of the DDR-400.
RAM bandwidth might slightly improve the performance of K8 in very rare cases, but the tighter RAM latency improves the performance of K8 in all cases.
October 20, 2006 12:03:12 PM

So a 667 CL4 is better than 400 CL3, right.
!