All 4 GB not visible? only 2.75

Discussion in 'Windows 64bit' started by Guest, Jun 26, 2005.

  1. Guest

    Guest Guest

    I have a Tyan K8WE (S2895) with 4 gigs of ram and a dual core opterons.

    When the computer first starts the boot screens show all 4 GB of ram are
    recongized, however once I'm into x64 the RAM shown on the System Properties
    screen (and Task Manager performance) is only 2.75. How can I access the
    rest of this RAM?
    Guest, Jun 26, 2005
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  2. Andre Da Costa [Extended64], Jun 26, 2005
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  3. Hmm, now I'm nervous how my installation of WinXP Pro X64 will
    handle 4 GB, because I have ordered 2 GB more last week.

    shows that x64 should be able to detect it.
    Thomas G. Madsen, Jun 26, 2005
  4. Andre Da Costa [Extended64], Jun 26, 2005
  5. Bios->NorthBridge: Memory Hole remapping by sofware -> ENABLED.

    et voila: 4 GB.

    Jose Manuel Tella Llop
    MVP - Windows
    (quitar XXX)

    Este mensaje se proporciona "como está" sin garantías de ninguna clase,
    y no otorga ningún derecho.

    This posting is provided "AS IS" with no warranties, and confers no
    You assume all risk for your use.
    JM Tella Llop [MVP Windows], Jun 26, 2005
  6. Guest

    M. Murcek Guest

    Can't speak for the Tyan board (I avoid 'em) but on my Asus K8N-DL, 4 GB RAM
    is present, and 4 GB is reported by x64 Edition.
    M. Murcek, Jun 27, 2005
  7. Guest

    Guest Guest

    Yeah - that's it -- the memory hole. Don't worry fellas... it supports 4 GB.
    I changed the memory hole setting in BIOS to Hardware (although Software
    probably works too). I think that the BIOS was reserving 1.25 gb for my
    nearly empty PCI slots.

    Easy fix.
    Guest, Jun 27, 2005
  8. Okay. Mine is a NCCH-DL board (also from Asus).
    Thomas G. Madsen, Jun 27, 2005
  9. Guest

    Guest Guest

    Windows XP x64 Edition supports up to 128GB ; on top of the 4GB space, there
    is some Hypertransport configuation space, which yields in some cases 3.9 GB
    on boards populated with 4GB.
    Note that the software hole remapping might be an issue if you do DMA IOMMU
    calls above 4GB ; you'll feel like an Intel user...
    Guest, Jun 27, 2005
  10. I sure hope that my motherboard supports 4 GB "out of the box"
    because I can't find a memory hole setting in BIOS.
    Thomas G. Madsen, Jun 27, 2005
  11. Well, it doesn't. BIOS only shows 3.5 GB and so does WinXP x86
    and x64.

    I have just found these words in the manual:
    "When all four sockets are populated with 1GB DIMMs (total 4GB),
    the system may detect only about 3.6+ GB (less than 4 GB) due
    to resource allocation of onboard devices".

    I can't understand why onboard devices need so much RAM allocated.
    Thomas G. Madsen, Jun 29, 2005
  12. Guest

    Sean M Guest

    Aren't those high addresses where PCI devices typically memory-map their

    -- Sean M
    Sean M, Jun 29, 2005
  13. I don't know. Maybe, but I don't have one single PCI device.
    The only non-onboard device I have, is my AGP graphic card.
    Thomas G. Madsen, Jun 29, 2005
  14. Guest

    Sean M Guest

    The same thing applies to AGP devices -- particularly graphics cards as they
    tend to map the framebuffer to a high region of x86 address space.

    -- Sean M
    Sean M, Jun 29, 2005
  15. Guest

    John Barnes Guest

    Ever wonder why the thing you mention happening, happen with any amount of
    memory installed, not just with 4 gig installed? :)

    John Barnes, Jun 29, 2005
  16. Hmm, I'm not very fond of having almost 512 MB RAM, that I can't
    use anyway, so at the moment I'm considering taking out two of the
    1 GB modules from my PC and changing them with 2 x 512 MB modules
    from my Apple G5. That should give me 3 GB RAM in my PC and 2,25
    GB in the G5. In my opinion it's better than having 4 GB installed
    in my PC but only 3.5 GB available.
    Thomas G. Madsen, Jun 29, 2005
  17. I sure wonder why :)

    Maybe I'm just stupid but I can't understand why I can have 2 GB RAM
    available, both in BIOS and Windows, with 2 GB installed, 3 GB RAM
    available with 3 GB installed (which I have at the moment) but only
    3.5 GB with 4 GB installed.

    The system allocates about 512 MB RAM to onboard devices with 4 GB
    RAM installed but does it mean that it's allocating nothing when
    there's only 2 or 3 GB installed for instance?
    Thomas G. Madsen, Jun 29, 2005
  18. Guest

    Sean M Guest

    It's not allocating any memory either way, it's giving the card(s) a block
    of memory for DMA operations. This causes the "memory hole" that you are
    experiencing, as any attempt to use that high-memory adddress will be
    remapped to the card.

    -- Sean M
    Sean M, Jun 29, 2005
  19. Ahh, okay.
    And the 'Memory Hole remapping by sofware -> ENABLE' setting tells
    Windows to manage that block instead of BIOS, or something like that?
    Thomas G. Madsen, Jun 29, 2005
  20. Here's an answer from Asus support.

    | This situation is caused by Intel 82875P MCH limitation and
    | other motherboards with memory hole remapping setting are
    | installed Intel 7xxx series MCH.

    I guess it means, that I'll never get a memory hole remapping
    feature on this motherboard, because of the 82875P northbridge
    Thomas G. Madsen, Jul 1, 2005
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