Comments on: Nehalem memory cheat sheet http://insidehpc.com/2009/04/13/nehalem-memory-cheat-sheet/ HPC News Without the Noise for Supercomputing Professionals | insideHPC Sun, 19 May 2013 10:46:54 +0000 hourly 1 http://wordpress.org/?v=3.1.1 By: PaulAdams http://insidehpc.com/2009/04/13/nehalem-memory-cheat-sheet/#comment-161614 PaulAdams Mon, 13 Apr 2009 14:50:23 +0000 http://insidehpc.com/?p=4386#comment-161614 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. 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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