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the new opteron have 4 mem channels per CPU. general guidelines for Intel Nehalem:

one DIMM in each mem channel results in 1333 Mhz more than 1 DIMM in each channel = 1066Mhz more than 2 per channel = 800 Mhz (max is 3 per channel for Nehalem Xeon 55XX)

thus the bandwidth is reduced by population

is there a similar recommendation or guide for AMD Opteron 6100 series?

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The Opteron 61xx series have 4 memory channels per CPU with 3 DIMMs per channel available, some rules of thumb;

  • load DIMMs equally across channels and CPUs
  • fill out the channels closest to the CPU first
  • put higher-ranked DIMMS closet to the CPU too
  • no more than 8 ranks per channel
  • the further away from the CPU you fill the slower the channel will work overall, so use fewer bigger, faster DIMMS more than more smaller, slower DIMMs for best performance.

There are exceptions but these are a decent starter, refer to you manufacturer's layout guide for more detail.

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  • As many DIMM's as possible
  • The highest speed possible.

;) THat is basically it. Not a lot of guidance needed here, or?

The details depend on exact chip and maybe motherboard (compatibility issues) and thus can not be answered here anyway ;)

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hi, do not think depends on motherboard. Channels per CPU and number of DIMM slots on server grade machines is same for all manufacturers HP, Dell etc –  John-ZFS May 12 '10 at 6:38
But the exact Dimm you can put in that will work may vary - this is why boards have compatibility lists. You may simply be unlucky with a particular ram brand and a particular board, even though theoretically it should work. –  TomTom May 12 '10 at 6:50
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