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  1. #1
    Join Date
    Aug 2003

    Asus P5B Deluxe w/WiFi - 4GB Mem not recognized

    Hello all,

    I recently upgraded my Corsair DDR2 C4 memory from 2 to 4 - 1GB sticks....however, the P5B DLX with bios (0507) only recognizes 3GB, not 4. I am running Vista which can go up to 16GB. As 3GB is stated in the bios, it passes that number into Vista...however, when I run CPU-Z, it shows all 4GB of memory. Any suggestions?

    Thanks so much!


  2. #2
    Member Epox4life's Avatar
    Join Date
    Mar 2005
    This is off ASUS's website...


    I have install total 4GB memory on my motherboard. However, it can only recognize around 3.1GB or less. My friend's SLI board even less than 3GB. What's up? How should I do to recognize 4GB totally?

    If you installed total 4GB memory, the system will detect less than 4GB of total memory because of address space allocation for other critical functions, such as:

    - System BIOS (including motherboard, add-on cards, etc..)
    - Motherboards resources
    - Memory mapped I/O
    - configuration for AGP/PCI-Ex/PCI
    - Other memory allocations for PCI devices

    Different onboard devices and different add-on cards (devices) will result of different total memory size.
    e.g. more PCI cards installed will require more memory resources, resulting of less memory free for other uses.

    On a SLI system, since PCI-Ex graphic cards will occupy around 256MB, another 256MB will be occupied after you install a 2nd PCI-Ex graphic card. Hence, 2.75GB memory left only if two SLI cards installed on A8N-SLI Premium while 3.0GB memory left with one graphic card without other add-on devices.

    This limitation applies to most chipsets & Windows XP 32-bit version operating system.

    If you install Windows XP 32-bit version operating system, we recommend that you install less than 3GB of total memory. If more than 3GB memory is required for your system, then below two conditions must be met:
    1. The memory controller which supports memory swap functionality is used. The latest chipsets like Intel 975X, 955X, Nvidia NF4 SLI Intel Edition, Nvidia NF4 SLI X16, and AMD K8 CPU architecture can support the memory swap function.
    2. Windows XP Pro X64 Ed. (64-bit) or other OS which can address more than 4GB memory.

    You can check below URLs for reference:
    i5 2500k @ 4.6GHz (24/7)

  3. #3
    Join Date
    Aug 2003

    Thanks for the reply, however...

    I looked at the 2 articles you have referenced...and they are way over my head..I understand the bios uses the extra 1gb of memory...but not sure why as when I run 3gb it doesnt allocated any to these functions......

    Can anyone tell me if there is a way around this running Vista? I was not able to see that in those 2 articles, at least that I could understand....

    Thanks again


  4. #4
    Senior Spellcheck greenmaji's Avatar
    Join Date
    Dec 2005
    It appears you need to enable the memory swap funtion..
    There should be settings in your bios to allow you to allocate 1Gb to system resorces and the remaining 3Gb (32bit XP's limit) to the OS.

    The charts and such are just explaining how that Gb of ram is being allocated to the system hardware.
    $300 for your CPU
    $500 for your GFX card
    $100 for your memory
    $200 for your motherboard
    $9.99 for your PSU

    Having a CHEAP power supply take out your computer PRICELESS.

  5. #5
    Join Date
    Aug 2003

    Running Vist which can recognize 16 GB


    Thanks for the reply...the problem is not with the OS as it is seeing just what is passed on from the bios...using Vista. The problem is that the bios is only showing 3, not 4gb.

    Vista using almost 1GB on my system just to load. I suspect that more and more people will have this question as they increase their memory with Vista.

    The problem is that the Asus P5B Deluxe can support up to 8 GB...I have 4 installed but the bios only is showing 3. Because of that Vista is seeing 3...I can run CPU-Z and that does see all 4, however I cant use it...HELP!


  6. #6
    Join Date
    Jun 2004
    Hi, sorry to revive such an old thread but I am having the exact same issue!

    I have a P5B Deluxe, and I have 4x 1gB Corsair XMS2 6400 CAS4 sticks of RAM, and the BIOS only recognizes 3072mB (3*1024). The sticks are all fine, my OS is Windows Server 2003 (32bit), and if I remove a stick I still have 3072mB showing up in my BIOS.

    CPUz however reports 1024mB in each slot. Why the heck does the BIOS need a gB of RAM to use for memory addressing when I have 3gB it doesn't need any? Can someone explain that to me, those articles are a bit confusing.

    And how come on server platforms 4*1gB works just fine and I get all 4gB? I don't want to install a 64-bit OS, is this not something a BIOS update could fix?

  7. #7
    Retired Joeteck's Avatar
    Join Date
    Oct 2001
    Long Island
    Modify your boot.ini. and add the /PAE switch.
    that should fix your problem.

    Your boot.ini should look simular to this one below.

    Click here for more info

    [boot loader]
    default=multi(0)disk(0)rdisk(0)partition(2)\WINDOW S
    [operating systems]
    multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Windo ws XP professional" /fastdetect /PAE

  8. #8
    Join Date
    Aug 2002
    CO, USA
    Microsoft says PAE is for MORE than 4GB of memory. You think that would still correct their problem? It looks like this is not related to the OS. The BIOS is reporting 3GB when there is 4GB, so the OS is just going to recognize what the BIOS reports.

    Sounds like greenmaji is onto something. Enabling a mem swap function?

  9. #9
    Join Date
    Jun 2004
    Quote Originally Posted by youngbuck
    Microsoft says PAE is for MORE than 4GB of memory. You think that would still correct their problem? It looks like this is not related to the OS. The BIOS is reporting 3GB when there is 4GB, so the OS is just going to recognize what the BIOS reports.

    Sounds like greenmaji is onto something. Enabling a mem swap function?
    I will try this, but I have read that you need a 64bit OS for that.

  10. #10
    Join Date
    Jun 2004
    Ok, I tried enabling memory swap remap in the Northbridge options, and now my BIOS recognizes 4096mB of RAM, but Windows crashes in loading. Turning it off, it works perfectly at 3gB of RAM... but I need that extra gB

    I will call ASUS and see what is up, I hope its not a logical limitation of the bored.

    I am running 32bit Win2003 Server btw...

  11. #11
    Senior Member
    DaveHCYJ's Avatar
    Join Date
    Jun 2003
    San Diego
    UPS just showed up. I'm also going from 2 to 4GB except with the Asus P5B Deluxe (non wifi). Same issue -- bios only sees 3008MB.

    Do post if you find the solution, and I'll do the same.

    Edit: Oh wow, I just revived a year old thread. Sorry about that -- I saw the date of the last post (10/19) which oddly enough is today and I didn't even bother to read the year. I'll search around on the forums some more to see if I can find the answer. I'd also be greatfull if someone posted it here as well.
    Last edited by DaveHCYJ; 10-19-07 at 02:53 PM.

  12. #12
    So even if it only recognizes 3gig will 4gig be used?

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