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Technology Stocks : Advanced Micro Devices - Moderated (AMD) -- Ignore unavailable to you. Want to Upgrade?

To: Joe NYC who wrote (196997)	5/16/2006 1:29:54 AM
From: dougSF30	Read Replies (1) \| Respond to of 275872

but the contribution will be CPU cycles, and in single digits, as far a CPU cycles are concerned. That is interesting about helping loads from cache, but reordering can move a load MANY instructions back, as I understand it, which could be 10-20 cycles or so, let's say. Also, K8's latency to main memory advantage is projected to shrink: With the numbers available to us now, we have reason to believe that the Athlon 64 X2's latency advantage will shrink to only 15 to 20%. For comparison, the memory subsystem of the Pentium 4 was almost twice as slow as the Athlon 64 (80-90 ns versus 45-50 ns). So that would put Core2 at, say, 60ns vs 50ns for K8, for main memory latency. Converting to cycles at 2.6GHz: 1 cycle = .38 ns, so: Core2: 158 cycles K8: 132 cycles If load reordering can save 10-20 cycles, that's a large portion of the difference between the two systems even during cache misses. Now, I don't know what the average reordering win is, and you may be right anyhow, that the biggest contribution comes from cache hit reordering.