WindowsXP is not recognizing my 4GB of RAM

I have Windows XP Pro installed with all the updates. I have an Asus P5ND2-SLI Delux motherboard (it takes DDR2 533 and 667 memory). I had 2GB of DDR2 533 memory; I removed those and installed 4GB of DDR2 667 RAM (Kingston KHX5400D2K2/2G). When Windows XP runs, it shows 2.25GB of RAM only!! The BIOS sees 4GB of RAM and I ran Asus PC Probe and it sees all four 1GB modules (a total of 4GB) ... what shall I do to get XP to see the 4GB of RAM? Shall I reinstall? Please, help! :(
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  1. Windows XP Professional 32-bit is limited to 4GB of address space. If you have 4GB of RAM installed, it will not show 4GB within Windows. What you'll probably get is the size of your pagefile subtracted from the 4GB.

    Some of this address space is reserved for hardware and the OS... so you'll never have access to the full 4GB anyway. If you want to access 4GB+ of RAM... your best solution is to pick up XP Pro 64-bit... but that will only work if your P4 CPU has EMT64.
  2. Good point, but my Page file is set manually to 4096 or 4GB but Windows XP sees 2.25GB of RAM; I will try disabling the Page File and see what happens. I did have Win XP Pro at one point, but compatibility with some drivers and software made me go back to the 32-bit system.
  3. You can also try enabling DEP if it isn't already enabled... this will also enable PAE which may give you access to all 4GB.
  4. I did disable the Paging System completely and enabled loading the Kernel into the RAM. I tried disabling and enabling combinations of the PAE and the DEP. XP is resilient and not seeing more than 2.25GB out of 4GB!!! Anyone knows what the significance of the 2.25GB is?
  5. I don't know that it has any significance... what I do know is that 32-bit XP will only see between 2 - 3GB of RAM when you have 4GB installed. I am unsure of all the causes behind it.
  6. The solution is easy, open up your boot.ini file in the root of your system drive. At the end of the line for your XP installation, add "/PAE" without the quotes. This enabled the physical address extensions which will allow you to use up to 4GB of memory (the upper limit in XP Pro).
  7. I have already done so and it does not see all the 4GB. I tried PAE and no PAE, DEP and no DEP, Paging File and no Paging file ... I guess I have to live with this! What a shame! I thought XP is able to recognize all 4GB of RAM regardless of the other mentioned items above! Oh well ... thank you for your help; truly appreciated! Is Vista any better in that regard!
  8. And I do not know if I was specific; but yes Zoron ... I did use the ini file to enable PAE without use; it only sees 2.25GB of RAM no matter what although my Asus PC Probe software sees all four 1GB modules from within XP!
  9. Weird, I know some motherboards don't support 4 GB, but since PC Probe sees it I would assume yours does. As I understand it, the architectures of Win2003 and WinXP are somewhat similar, I have a Win2003 box with 6GB of memory and it sees all of it just fine. I did have to enable PAE, before PAE it would only see 3.87 GB. Maybe that's a question for a Microsoft newsgroup.
  10. If your system sees 6GB of RAM, then you are running Win 2003 64Bit; the 32bit system will not see beyond 4GB. You are probably right; Microsoft is probably the only people that would know. I wonder if it helps reinstalling Windows XP ...
  11. Quote:
    If your system sees 6GB of RAM, then you are running Win 2003 64Bit; the 32bit system will not see beyond 4GB.

    Nope, 32-bit goes past 4GB just fine...
  12. If you are using a 32Bit system, then it may recognize 6GB (using PAE) but will use only 2GB at a time:

    I think I will install XP pro 64 and get this over with. Thanks for all the help.
  13. Quote:
    If you are using a 32Bit system, then it may recognize 6GB (using PAE) but will use only 2GB at a time:

    I think I will install XP pro 64 and get this over with. Thanks for all the help.

    wont make any difference im running XP pro x64 on an Intel board wihich support 4gb ram and hey guess what it says i only have 2.25gb ram

    not fussed though as done various benchmark test that show its using the 4gb ram

    just seems to be one of the many glitches in windows
  14. Don't reinstall Windows, it doesn't help. I bought 4GB of RAM right away when I bought my system and freshly installed XP home on it and it only recognizes 2.25GB of RAM.

    I don't have a problem with it showing that amount. The only problem I would have if it fails to use all 4GB.

    Does anyone know how much it uses?
  15. 2.25 Gigs is too low to be considered the regular issues Windows 32-bit has with the ammount of memory you have (should be around 3-3.5GB based on what I saw in my system and other threads). There is some other issue with your setup: check BIOS settings and such for settings pertaining to how memory is presented to the OS.
  16. Yeah 2003 server (and 2000 with a config change) support up to 8Gb of RAM on the 32bit version of the O/S by cheating.

    They both actually support 4Gb natively (32bit max) but use part of the memory space between 3Gb & 4Gb to hold additional register information so that the 4Gb - 8Gb memory areas could be accessed.

    In principle it is possible to do the same on xp, we had some Microsoft Consulting Services people in a while ago who did a really cool demo of how any version of windows could be turned into another with re-registering a few dll's (there was allot more to it than that) but the specifics of what they were trying to show was that we could do our server based testing on workstations by forcing the missing elements into xp pro (if this wan't Microsoft I'd be thinking license violation!).

    Anyway to cut a long story short have just builty a new PC with 4Gb and did not have a copy of XP 64 to hand so just wacked on 32bit version hitting the same problem.

    Anway spoke with Routon (the very scary MS man) and he is going to send some instructions on how to extend up to the full 4GB on 32bit.

    I know they are only of use for 10 days until Vista arrives but I will post when I receive.
  17. Awesome!

    It will be really helpful when I get into playing the major multi-threaded video games. I figure one stick of RAM per processor (I'm on a Quad Core).
  18. I know this is a bit old of a post by you, but the OS you use is made to use up to 32GBs of RAM as specified by the MS Knowledge base:

    "Windows XP Professional and Windows Server 2003 Memory Support. The maximum amount of memory that can be supported on Windows XP Professional and Windows Server 2003 is also 4 GB. However, Windows Server 2003, Enterprise Edition supports 32 GB of physical RAM and Windows Server 2003, Datacenter Edition supports 64 GB of physical RAM using the PAE feature."

    As you can see from your image you posted, you are using this version. So your response doesn't follow.
  19. Bottom line..... Windows XP will ONLY recognize/utilize 2 GB of RAM. Sorry man. :( It might SAY 4 GB. But will only USE 2 GB.
  20. not it does not use only 2, it will use 3 and your hardwares will use 4

  21. I know this is old post but I have a similar question with different results.

    p5nd2-sli, p4 945 oc 3.9, xt600, 4gb of ram pc5700
    dual boot with vista and xp

    "vista is way slower"

    anyway I have done nothing like you guys said. I really don't understand what you were even talking about. SYSTEM says 3.5 gb of ram?

    why do you guys have 2.5 and I have 3.5.
    No I am not running 64bit. original install was xp pro sp1, upgraded to sp2

    I would love to get it to recognize all 4gb
  22. XP can only see 3.0 but your processor will use 4 ;)

    vista I think can see more.

    unless sp3 for XP changes something XP can only see the 3 for now and you are all good to go as far as your XP is concerned
  23. A 32Bit system can't address more than 3GB of ram. Doesn't matter how much you tweak or change the OS. 32bit is 32bit. To utilize 4GB ram or more you'll have to install a 64bit OS.

    What most companies do when they deliver 4GB ram with a 32bit OS is that they share 1GB ram to the graphics card.

    End of story ;)
  24. I have 3gb and xp 32bit, and average 2.25 gb with my own programs before errors. I would guess something is missing a knows it if hardware is communicable the way they see fit.

    I have buried mine with an xp test from resource tools to 7gb in xp 32. even my own scripting in 1990s C language has a means to bury all the ram...the way it errors isn't nice, but neither is the language :)

    it has been a screw up for some time now. 32 bit or not, 4gb is 4gb, let it have it. Hyper threading etc would not exist if it did not get more than the average it 32bit or 64, there is a software problem if it cannot use it.

    yep. Xp is the problem...

    just go back yonder youth to the past to an extinction called win98 and never wonder why there is a problem again... :pt1cable:
  25. The *problem* is that Microsoft has restricted the total address space to 4GB in xp and vista for compability and other reasons. Other 32bit systems that don't have these concerns have not problem using 4 or more GB - given that the hardware supports it, of course.
  26. XP and Vista both will use upto 4 Gigs of ram (2 to the 32nd power).
    The problem is that this is the max ram addresses, SO if you have a 512 Meg video card this memory is mapped to the upper portion of the 4 Gigs this would leave about 3.5 Gigs ( there are some other small IO's that are also mapped here.

    My system EX Pro System info shows 4 Gigs and 3.5 Gigs avail ( I have a 512 M video card (If you have a 1 Meg video card then this would leave only 3.0 avail)

    Now you have to subtract all the programs/applications that are running and what is left is then "Available" for use. Under Windows task manager I show:

    Total = 3.406 ( my 512 GPU is subtracted from the 4 .0 Gigs)
    Available = 2.6 Gigs (3.4 minus the processes that are running)

    Get the general drift

    NOTE: In terms of memory, the only advantage on a 64 bit /with 4 gigs RAM is that you do not loose the Space for REmapping Graphics memory. AND you can have more than 4 gigs Ram
  27. From MS 64 Bit website...

    Understanding 64-bit PCs
    If you're shopping for a new PC you're probably going to come across systems that are designated "64-bit." These are computers running 64-bit editions of Windows Vista, typically with 4GB of memory or more. Compared to 32-bit systems, which top out at around 3GB of memory, 64-bit PCs offer added responsiveness for people who are running a lot of applications at the same time and switching between them frequently.

    Pat Strobel
  28. RetiredChief said:
    The problem is that this is the max ram addresses, SO if you have a 512 Meg video card this memory is mapped to the upper portion of the 4 Gigs this would leave about 3.5 Gigs ( there are some other small IO's that are also mapped here.

    RetiredChief has pretty much posted with what I found when researching this recently. This is a pretty good article which explains what is happening.

    ~Dan (Not the same Dan as the article author)
  29. My Win XP Pro 32 bit machine has 4 GB of system ram installed, and no other PCI cards except video. With that setup:

    1. With a single video card with 512 MB of ram, Windows registers 2.75 GB of ram.
    2. With 2 256 MB video cards in SLI mode, it registered 2.5 GB of ram.

    So, the people that are saying that Windows should be reading closer to 3-3.5 GBs, I don't agree with you.
  30. MS explicitly states that Windows XP 32bit is limited to 4GB RAM.

    MS also says that the /PAE switch is available on XP, but it is only available to allow Data Execution Prevention, not to increase RAM beyond 4GB.

    I have an IBM T60p thinkpad running 32bit XP Pro with 4GB of ram but I only see 3.0GB. So I'm missing 1GB. The concensus I get from several other blogs is the Intel p45 Chipset on this laptop limits what the OS is able to see to 3GB.

    Some of my colleagues hae the IBM T61p laptop. It has the intel p65 chipset, and my colleagues say it sees all 4.0GB.

    These numbers are despite the fact that both laptops have a 512MB Video card.

    I think some chipsets may limit the actual RAM windows sees. Also I hear windows properties sometimes says 4GB when task manager will report 3.5 or less. Physical RAM is not always shared with the video card so don't expect that to always crop your physical ram number.
  31. My Comp is having the same issue.. i added 2G and replace a 512bit, so from but when i go to my setup it reads 4.50G and yet my properties shows 3.5 and it use to be 3.24
  32. Necropost
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