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    SubjectRe: Opteron box and 4Gb memory
    J.A. Magallon wrote:
    > Hi...
    >
    > I have some Quad-Opteron boxes with 4Gb memory and two of them are
    > running two different Linux distros.
    >
    > Box one sees 4Gb of memory, but box two just sees 3.
    > Their mtrr setups are different:
    >
    > Why ? Is it a bios setup problem ? A kernel problem ?
    > grep HIGHMEN in configs for both kernels does not give anything, so
    > I still understand less this thing...
    >

    It would depend on how the BIOS programmed the memory controllers. For
    32-bit (and lots of device) compatibility, a memory hole is required
    below 4 GB. Not all memory controllers can remap memory in the 3-4 GB
    range above the 4 GB memory; I'm not sure if that varies with the
    different Opteron processors.

    Also, if you run a 32-bit distribution, you need to have HIGHMEM_64G
    enabled in the kernel.

    -hpa
    -
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