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    SubjectRe: lost memory on a 4GB amd64
    Date
    Hi Sergei,

    I have the same board with 4Gb ram running a 64bit 2.6.8.1 and solved it by
    changing something in the bios. Let me reboot and I'll take a note of what I
    did...

    On Thursday 16 Sep 2004 05:48, Sergei Haller wrote:
    > Hello,
    >
    > A friend of mine has a new Opteron based machine (Tyan Tiger K8W with two
    > Opteron 24?) and 4GB main memory.
    >
    > the problem is that about 512 MB of that memory is lost (AGP aperture and
    > stuff). Although everything is perfect otherwise.
    > As far as I understand, all the PCI/AGP hardware uses the top end of the
    > 4GB address range to access their memory and there is just an
    > "overlapping" of the addresses. thus only the remaining 3.5 GB are
    > available.
    >
    >
    > Now there is an option in the BIOS called "Adjust Memory" which puts a
    > certain amount of memory (several choices between 64MB and 2GB) above the
    > 4GB address range. I tried the 2GB setting which results in 2GB main
    > memory at addresses 0-2GB and 2GB memory at addresses 4GB-6GB.
    >
    > the problem is that the kernel (2.6.3-9mdksmp and vanilla 2.6.8.1) crashes
    > if this option is enabled as soon as some memory expensive program is run
    > (e.g. X)
    >
    > I've seen some postings on the net talking about some "kernel patch" for
    > some "memory split", but nothing more specific. Do I just need a certain
    > patch to get it working or is there more to it?
    >
    >
    >
    > BTW, the memory map displayed at boot is
    >
    > BIOS-e820: 0000000000000000 - 000000000009fc00 (usable)
    > BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved)
    > BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
    > BIOS-e820: 0000000000100000 - 00000000d3ff0000 (usable)
    > BIOS-e820: 00000000d3ff0000 - 00000000d3fff000 (ACPI data)
    > BIOS-e820: 00000000d3fff000 - 00000000d4000000 (ACPI NVS)
    > BIOS-e820: 00000000ff780000 - 0000000100000000 (reserved)
    >
    > if I leave the 4GB memory in one chunk and
    >
    > 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 - 0000000180000000 (usable)
    >
    > if I enable the "adjust memory" option and split the memory in two 2GB
    > blocks.
    >
    > Thanks in advance,
    >
    > Sergei
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