A8V Deluxe Won't See 4gb of RAM

Discussion in 'Asus' started by Ryan Tremblay, May 31, 2006.

  1. I bought some more RAM for my computer so I can do some video editing on it.
    I bought 2 Corsair Twin XMS 1024-3200. I popped it into my computer and
    when I turned it on I noticed the MB only saw 3600 MB of it then I got a
    message saying USB overcurrent detected! System shutting down in 15
    seconds. I took two of the two sticks out and it ran fine with 2GB I tried
    switching the memory and it worked only with 2 GIG. I was thinking maybe it
    was the motherboard so I have another computer with the same mobo same
    problem and error message and I have nothing USB running on it. The memory
    has a timing of 3-3-3-8 do I need to edit my memory settings manually for my
    BIOS to see it and run happily? I do have the latest BIOS (1017) I do not
    want to try the Beta one just in case something happens. Has anyone else
    seen this problem and if they did what was the fix? Any help would be

    Ryan Tremblay, May 31, 2006
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  2. Ryan Tremblay

    DaveW Guest

    You have just discovered a known problem with most/all current motherboards.
    They can accept 4 GB of RAM sticks, but the design engineers have not
    perfected their actuall being able to be fully used. 3.6GB of RAM seems to
    be the current limit.
    DaveW, May 31, 2006
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  3. Ryan Tremblay

    Paul Guest

    I see that is also reported in this forum. I expect this is a BIOS
    issue, and not a hardware issue as such. The BIOS memory map is
    probably being set up incorrectly, and some of the BIOS code
    is screwing up hardware when it thinks it is writing to memory.
    If the writes go to some USB interface registers, maybe that is
    how the motherboard ends up thinking there is a USB overcurrent


    (the forum topic list is here)
    http://vip.asus.com/forum/topic.asp...el=A8V Deluxe&page_size=100&page=1&count=1447

    I think I'd try a previous BIOS, depending on how many of them
    are still available on the web site. Also, you should report
    your problem to Asus tech support, because Asus may not read the
    stuff posted on their own forums.

    As for how memory works on an AMD system, without any intervention,
    there is a need to reserve some address space for addressing bus
    devices, like PCI bus/AGP bus/PCI-Express bus. On some motherboards,
    the amount of address space needed is quite large (only slightly less
    than 3GB of memory can be used on an SLI board with two video cards).
    With 3.6GB reported, you are doing quite well.

    There is a memory mapping capability in the AMD processor, and it allows
    the memory and I/O space to be remapped. (You should look in Google,
    for terms like "memory hole", "PAE", and the like, and also look
    for which OSes support addresses above the 4GB mark.) This capability
    exists in the AMD processors, but the BIOS has to be modified to get
    the support. The memory hole issue is not documented in the user
    manuals, because Asus adds the support after the fact (like the
    fifth BIOS release or so). With WinXP, I would expect the 3.6GB of
    memory you are currently seeing, is all you are going to get. If
    you were using a 64 bit OS, and the BIOS has a "memory hole"
    setting and it is enabled, then you'd be able to use the whole
    4GB of memory.

    (Sample discussion of large memory on AMD systems.)

    So, your "USB overcurrent" issue is a definite BIOS bug. The
    vip.asus.com forums have some other reports of USB overcurrent.
    The memory issue is common to a lot of boards - the fact that you
    got 3.6GB of memory to show up, implies you don't have an AGP card
    installed, because I thought with AGP present, even less memory
    would show up. It is either that, or the AGP aperture is set quite
    low. But it will be pretty hard to look in the BIOS for the
    "memory hole" setting, until you get a BIOS loaded that doesn't
    have that "USB overcurrent" bug.

    Post back what you find.

    Paul, Jun 1, 2006
  4. Ryan Tremblay

    Bob Knowlden Guest

    I take it that you're running 32 bit Windows XP.

    Because of limitations (that I don't fully understand), 4 GB of RAM never
    appears in XP. 3.6 GB is more than what I've seen listed on some Dell
    workstation PCs at my employer.

    XP64 does not share this limitation, but changing to it is not trivial. (A
    clean XP installation is required, rather than an upgrade, and some
    peripherals don't have 64-bit drivers available.) 64 bit Windows Vista might
    be a good choice, although it isn't supposed to be available until early
    2007. I'll leave discussion of Linux to those who are familiar with it.

    Here is Asus' take on it:


    (It's not a prime example of clear writing.)

    You should also be aware that the A8V Deluxe may run your RAM at 333 MHz
    (rather than 400) when all four DIMM slots are filled:


    The FAQ suggests manually setting the memory frequency. You may not be able
    to use the 1T command rate, though.

    Address scrambled. Replace nkbob with bobkn.
    Bob Knowlden, Jun 1, 2006
  5. The problem here, is that a 32bit processor, or a processor running in
    simple 32bit mode, can only address 4GB. Now unfortunately, things like
    the BIOS, video cards, network cards etc., all need windows into this area
    to work, and hence you can't have 4GB of visible RAM. Now the crash, may
    be because some systems get confused about the mapping of the memory, when
    they have things like the USB I/O area, 'overlapping' an area of memory,
    and unless this is properly handled, this can result in crashes. There can
    also be drive problems with having all four memory sockets filled,
    depending on the age of your processor...
    Seperately, it is possible for a 32bit system to address more memory,
    using 'PAE'. Effectively a system like the old 'bank switching' for
    memory. PAE, requires a whole 'set' of things to work. A system with a
    chipset that supports it, a BIOS that implements the handling for this,
    and an OS, that understands how to use this (and in fact implements larger
    address tables for the resources - this imposes a slight 'overhead'
    associated with doing this). Now the 'joke', is that Microsoft have
    elected (deliberately...), not to allow this to work in XP home or Pro.
    W2K, supports this, XP Server supports, and XP, with the original SP1,
    without any hotfixes, also supported this (they turned 'on' support for
    PAE at this point). However they then left PAE enabled (it is also used
    for certain security features in latter processors), but deliberately
    prevented the handling of memory beyond 4GB, with latter 'fixes'...

    Best Wishes
    Roger Hamlett, Jun 1, 2006
  6. Ryan Tremblay

    Ken Guest

    All this is just another example of MS's failure over the various
    incantations of the product series to use the features available in the
    processor. IBM provided as much, if not more, than is currently
    available with their OS/2 product. They just couldn't market what they had.

    Windows, IMO, is not an operating system. It is a user experience
    coupled to a huge collection of applications that have to survive in the
    product provided.

    Bank switching is hardly untried technology. I had it on a 286 machine
    running CP/M and Desqview. That (and I) are older than snot. I'm not
    reminiscing for the 'good old days' but I also realize how short XP
    falls in what the basic hardware can provide.
    Ken, Jun 1, 2006
  7. Ryan Tremblay

    DRS Guest

    Where do you get those numbers from? In SLI mode the two video cards are
    seen by the system as one "super-card". This has been discussed before.
    Depending on your system configuration most people would expect to see
    3.5GB - 3.75GB.
    DRS, Jun 1, 2006
  8. Ryan Tremblay

    DRS Guest

    Expected behaviour.
    Not expected behaviour.
    DRS, Jun 1, 2006
  9. Ryan Tremblay

    Paul Guest

    "recognizing 4GB..."

    Both video cards have their own area in the memory map. "Logically"
    they may appear to the system as one "super-card", but the video
    card driver knows both cards do work, knows half info goes to one
    card, and half to the other. The driver hides the details.

    The first post in this thread, is from someone who tried a couple
    PCI Express video cards on a 4GB system.


    The numbers are all over the place here. I believe the guy is
    using a 64 bit OS, and he doesn't get his full 4GB until he
    removes one of his two video cards. And that was with "memory hoisting"
    (memory hole) enabled.


    Paul, Jun 1, 2006
  10. Ryan Tremblay

    DRS Guest

    As he rightly points out, "I know this is usualy a chipset limitation that
    reserve some memory, but on
    normal board it would make 3.5-3.8 GB available."

    I've posted this before but it's worth repeating:
    Q: Why does the system only show 3.5 GB of memory when I have 4.0 GB of
    memory installed?

    A: Under the current PC memory addressing, there is a memory area just below
    4.0 GB which is reserved permanently. The reserved area is for system BIOS
    to put APIC, ACPI Table, PCI Devices', Resources and AGP aperture
    information. When your system DRAM is 3.5 GB or lower, the system will show
    that the same amount of memory has been implemented. However, if the system
    DRAM is above 3.5 GB of memory, the actual amount of memory that the system
    shows will be less due to the reserved area. Regardless of memory size, the
    reserved memory addressing is always present, but only when the DRAM rises
    above the 3.5 GB amount will that area become visible.

    DRS, Jun 1, 2006
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