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    SubjectRe: Missing RAM on x86_64
    Mike Richards a écrit :
    > Hi, I appear to be missing quite a bit of RAM on an x86_64 system. I
    > have 1GB installed, but 'free' only shows 878MB:
    >
    > pokey$ free -m
    > total used free shared buffers cached
    > Mem: 878 571 306 0 52 332
    > -/+ buffers/cache: 186 691
    > Swap: 1023 0 1023
    >
    > I'm used to seeing a little bit of RAM missing with 32bit systems, but
    > 146MB seems a bit much. The part of dmesg that concerns the RAM is
    > shown below. Anyone know what's up here? Is this normal for an x86_64
    > system?
    >
    > Linux version 2.6.20.11 (root@pokey) (gcc version 4.1.2) #1 SMP Thu
    > May 24 18:29:52 GMT 2007
    > Command line: auto BOOT_IMAGE=2.6.20.11 rw root=801
    > BIOS-provided physical RAM map:
    > BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
    > BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
    > BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
    > BIOS-e820: 0000000000100000 - 0000000037fd0000 (usable)
    > BIOS-e820: 0000000037fd0000 - 0000000037fde000 (ACPI data)
    > BIOS-e820: 0000000037fde000 - 0000000038000000 (ACPI NVS)
    > BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved)
    > BIOS-e820: 00000000fee00000 - 00000000fef00000 (reserved)
    > BIOS-e820: 00000000ff780000 - 0000000100000000 (reserved)


    I would say your BIOS needs an update or some tweakings.

    The (usable) parts that it gives to the OS (linux) are :

    0000000000000000 - 000000000009fc00
    0000000000100000 - 0000000037fd0000

    Thats not 1024 MB, but 892 MB

    Here is the output on a 16 GB x86_64 machine

    BIOS-provided physical RAM map:
    BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
    BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
    BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
    BIOS-e820: 0000000000100000 - 000000007fff0000 (usable)
    BIOS-e820: 000000007fff0000 - 000000007ffff000 (ACPI data)
    BIOS-e820: 000000007ffff000 - 0000000080000000 (ACPI NVS)
    BIOS-e820: 00000000ff780000 - 0000000100000000 (reserved)
    BIOS-e820: 0000000100000000 - 0000000480000000 (usable)

    On node 0 totalpages: 2097039
    On node 1 totalpages: 2097152

    total of 4194078 pages (while exact 16GB should be 4194304 pages)


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