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Incorrect Memory Size shown under WinXP system properties

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by vilicial

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I have 4GB RAM installed on my Intel P4 Cor2Duo 1.86MGz system. While the POST counts the full 4GB RAM, only 3GB is shown under WindowsXP Pro system properties. Can you give an expanation why this may be so? What is the maximum size WinXP can display under system properties?

9 replies

by langr

Here's what I believe is happening: Windows XP only recognizes a maximum of 4 GB of memory. However, this INCLUDES the virtual memory used by the pagefile system.

Check your pagefile size - if you add this to the number reported by system properties, it should total your 4 GB.

I'd recommend turning off virtual memory/pagefile system on your system with 4 GB of physical memory:

1. Start the Control Panel System applet (go to Start, Settings, Control Panel, and click System).
2. Select the Advanced tab.
3. Under the Performance section, click Settings.
4. Select the Advanced tab.
5. Under the Virtual Memory section, click Change.
6. Select No Paging File and click Set.
7. Click OK.

You may also want to take a look at this memory tweak guide: http://www.techspot.com/tweaks/memory-winxp/

by vilicial

Hi Langr - Thank you for your explanation and advice

by older mycroft

What did you hope to achieve by installing 4GB on an XP OS?

I thought that 1MB was optimal, 2MB was exceptional and anything above that would produce little gain for the strain (on your wallet).

The Law of Diminishing Returns and all that stuff. Not exactly an Economics symposium but the principle is the same.

*EDIT* Just a thought: if it were Windows x64 you could install up to 128GB, I believe.

by thechas

Beyond any limits for XP, there are limits for the amount of RAM that 32 bit system hardware can address.

In fact, there is a good chance that your BIOS is telling you a white lie about how much memory you do have.

Now, your hardware can indeed address 4 GB of RAM. However, the chip-set manufacture requires that at least 750 MB of the upper section of RAM addresses be reserved for what can best be described as system housekeeping functions.

These upper RAM addresses is where the firm-ware in the chip-set along with the BIOS service the hardware on the motherboard.

So what is happening, is that your BIOS is reading all of your installed RAM, then throwing away the top 1 GB so that Windows won't try to use it.

There are no work-arounds or fixes. The only way to have more than 3 GB of active RAM is to have a 64 bit system running a true 64 bit operating system.

Chas

by vilicial

Thank you Old Mycroft. It was just outright ignorance that made me install 4GB on an XP OS machine. I believed there will be a dramatical performance improvement by having as much memory as I could since the mainboard supports upto 8GB. From your explanations, I now understand it was a foolish thing to do if that amount of RAM just sits there doing nothing. Thank you once again for giving me an insight in this regard.

by vinod1259

Hi,

In windows Xp maximum ram supported limit is 4GB.please check the below mentioned 2 things..i hope it will helps to fix ur problem.

1) The PAE kernel is not enabled by default for systems that can support more than 4 GB of RAM.

To boot the system and utilize PAE memory, the /PAE switch must be added to the corresponding entry in the Boot.ini file. If a problem should arise, Safe Mode may be used, which causes the system to boot using the normal kernel (support for only 4 GB of RAM) even if the /PAE switch is part of the Boot.ini file.

The PAE mode kernel requires an Intel Architecture processor, Pentium Pro or later, more than 4 GB of RAM, and Windows 2000, Windows XP, or Windows Server 2003.

The PAE kernel can be enabled automatically without the /PAE switch present in the boot entry if the system has DEP enabled (/NOEXECUTE switch is present) or the system processor supports hardware-enforced DEP. Presence of the /NOEXECUTE switch on a system with a processor that supports hardware-enforced DEP implies the /PAE switch. If the system processor is capable of hardware-enforced DEP and the /NOEXECUTE switch is not present in the boot entry, Windows assumes /NOEXECUTE=optin by default and enables PAE mode. For more information.

Refer the below mentioned boot.ini file which has PAE enabled

[boot loader]
timeout=0
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /PAE /NoExecute=OptIn

2)refer this link :
http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx

for furuther information :
Refer:
http://www.microsoft.com/whdc/system/platform/server/PAE/PAEdrv.mspx

http://www.microsoft.com/whdc/system/platform/server/PAE/pae_os.mspx

by manny

HP servers are notorious for showing only 3.5gb with 4gb of installed memory. The motherboard is reserving 512MB for PCI functions.
The PAE has nothing to do with displayed memory. It simply allows the OS to access more of it.
So while yes you have 4gb of installed RAM, Windows will only use whatever the mobo allows it.

by retro77

Check this out: http://www.dansdata.com/askdan00015.htm

Very in depth...

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