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XP won't recognize full 4GB of Memory

By rahkstah
Nov 21, 2007
  1. I just recently built a new pc and added 4GB G-Skill DDR2 800 Dual-Channel memory.

    On the post screen, the bios recognizes the full 4086MB.

    Sys info only recognizes 3.5GB of the memory, yet my diagnostic tools say that my PC is running on 2048MB.

    I've been searching, and reading, a lot about this issue, and I don't fully understand why it's doing this.

    Windows XP Home SP2
    AMD Athlon 64 X2 6000+
    Gigabyte Mobo

    Heeeelp! Thanks in advance guys.
     
  2. Teranius

    Teranius TS Rookie Posts: 115

    im not certain either, but im guessing the missing ram is being held in reserve by your OS. the same thing happens with harddrives, for instance i have a 320gig hd but my OS only picks it up as 300gig
     
  3. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    This is a limitation of 32-bit operating systems. Without a special boot option, Windows allows userland programs to use only up to 2GB of RAM, rest is for kernel use only. Since you can address only 4GB of memory with 32 bits, some of your RAM is masked by other system resources like video memory that has to be accessed too and will take out a chunk of the address space,making some of your RAM unusable.

    If you want to make full use of your RAM, you have to install a 64-bit OS.
     
  4. rahkstah

    rahkstah TS Rookie Topic Starter

    I was afraid of that. Thanks Nodsu.
     
  5. Sukami

    Sukami TS Rookie

    ummm.....

    also couldn't he turn off virtual memory and get closer use to the 4GB mark

    Just wondering....
     
  6. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    Uhm.. Virtual memory is the cornerstone of modern operating systems. You can't turn it off :)

    Maybe explain a bit more?
     
  7. Teranius

    Teranius TS Rookie Posts: 115

    you could lower your virtual memory, but thats not always the best idea as it has an impact on your performance
     
  8. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    ...

    Really do explain a bit more. Obviously I have been miseducated and have some kind of a wrong idea of virtual memory.

    Wat does this "lowering" do and how does it help with the address space provided by 32-bit CPUs?
     
  9. Daveskater

    Daveskater Banned Posts: 1,687

    it sounds to me that if you lower the virtual memory amount then windows would be able to see more of your physical memory but i'm not sure if you can turn virtual memory off or not, but you should be able to lower its size easily enough

    i haven't tried this because my mobo only supports 1gb of ram ;)
     
  10. Sukami

    Sukami TS Rookie

    you can shut it off read up on it.....and as lon as he has good ram 4GB he should be good
     
  11. Didou

    Didou Bowtie extraordinair! Posts: 4,274

    Lots applications will completely refuse to launch or even install if Virtual Memory is deactivated.
     
  12. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

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