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Nehalem memory cheat sheet

Doug at ClusterMonkey pointed us to a Nehalem memory cheat sheet put together for Dell’s technology wiki by Jeff Layton. The writeup looks like a pretty complete summary of the various options for configuring memory on a Nehalem, and what the impact of the various options is on memory performance.

Comments

  1. Summary:
    * 1 bank x 3 memory channels per socket is 1333 MHz memory (if CPU supports it)
    * 2 banks x 3 memory channels per socket is 1066 MHz memory
    * 3 banks x 3 memory channels per socket is 800 MHz memory

    Thus, if you are going for large memory capacity, you can lose a large amount of memory bandwidth. For example, if you choose 8 GB RDIMMS and populate 2 banks x 3 memory channels, you can get 96 GB of memory with an 8.5% loss in bandwidth.

    If you choose 4 GB RDIMMS and populate 3 banks x 3 memory channels, you can get 72 GB of memory with an 22% loss in bandwidth. Or you could go with 8GB RDIMMS for 144 GB of memory, but still with the 22% loss in memory bandwidth.

    Since I like to purchase large memory systems at work, this turned out to be an eye opener for me. Thanks for digging this up.

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