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I noticed that one of our Windows XP 32-bit boxes, which has 4GB of RAM, will only use up to 1.3GB of physical memory. Has anyone run into this before?

The only thing I can think of is that it's a 4GB-on-32-bit-OS thing, but I don't see why that would cause XP to only use 1/3 of the RAM.

Thanks!

In answer to your questions:

  • The OS displayed 3.25GB of RAM.
  • Even under high load (i.e., Photoshop + Firefox + other RAM-intensive programs) the system (according to procexp) only used up to 1.3GB of RAM. RAM load stayed at about 33%.
  • I just swapped out one of the 2GB sticks for 1GB, bringing me to 3GB of RAM. Windows XP says I have 3GB of RAM installed. But procexp reports only 750MB being used, or about 25% of RAM.

So it doesn't seem to be a 32/64 bit issue.

The box has a Wolfdale E8400 running on an Asus P5K SE mobo. The OS is Win XP SP3 32-bit.

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have you tried to swap out all the ram? maybe it is faulty? tried to run a memory test or something? –  Svish May 30 '09 at 16:22
    
I swapped out one of the RAM sticks. I also ran Microsoft's memory test before and after I swapped the stick, and it passed all the tests. So it's probably not faulty RAM. –  user4318 May 30 '09 at 17:20
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4 Answers

What does the computer BIOS say about the available RAM? Also, what do you mean by "will only use up to 1.3 GB"? How much memory does it say the computer has in System Properties?

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It said 3.25 GB in System Properties, but the RAM load would only go up to 1.3GB, even with multiple RAM-intensive programs open. –  user4318 May 30 '09 at 16:26
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32 bit will make it stop out at about 3.25GB.

Does it go into swap file overdrive when it hits that ceiling (and did you remember to configure the swap file to either auto-adjust its size or fix it at 4 GB?)

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32-bit CPUs support up to 4 GB of RAM, of which about 3.2 GB is available to the OS. (If the CPU has PAE, then the theoretical maximum is 64 GB, though Windows XP is artificially capped at 4 GB). So bitness shouldn't matter.

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Take a look at the following page from MS. Especially the top table.

http://msdn.microsoft.com/en-us/library/aa366778.aspx#physical_memory_limits_windows_xp

Each process can only have 2GB, the kernel will only use 1GB.

What are you running on the box? If it's only the one program, you won't be able to use all the 4GB.

See if it makes more sense after reading the page.

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