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Thread: dual core x2. able to provide some benchmarks between single and dual channel mem int

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  1. #1
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    Feb 2005
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    In theory the performance degradation by switching to single channel should escalate with dual vs. single cores because the dual cores are sharing the 128-bit memory bus (whereas a pair of single core opterons would each have their own full 128-bit memory bus). By further cutting the memory bus width in half (to 64-bit) by using a single channel interface, you might starve the cores at higher speeds. Here is AnandTech's explanation:

    Historically, the Athlon 64 hasn't really been memory bandwidth bound, since the move to Socket-939, which gave it a full 128-bit wide memory bus, and more bandwidth than these CPUs could use.

    With the move to dual core however, the effective memory bandwidth that each core gets is significantly reduced, as they both have to share the same 128-bit wide memory interface normally dedicated to a single processor.


    I think that explains why in real world performance, Socket 939 CPUs see little real-world gain in performance with increased memory bandwidth, and why 754 show more real-world gain in performance with a similar percentage increase in bandwidth.
    Last edited by p0tempkin; 07-13-2005 at 08:46 AM.

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