WindowsXP Pro won't recognize 4GB of memory.

[nmX.Memnoch]

Ahhh...thanks for the explenation.

So would it be turned off if you had NoExecute=AlwaysOff in the boot.ini? Not that I want it off...I'm just curious.

[Camarade_Tux]

In fact, under XP SP2, even without DEP-capable CPU, 32-bit but with 2GB RAM, PAE gets enabled.

You can circumvent this by specifying which kernel windows should load in boot.ini.

[cluberti]

Ahhh...thanks for the explenation.

So would it be turned off if you had NoExecute=AlwaysOff in the boot.ini? Not that I want it off...I'm just curious.

It should, yes, although sometimes you do have to specify that it loads a non-PAE kernel specifically in boot.ini.

[cluberti]

But if you have a 64-bit capable processor, but 32-bit WinXP installed then WinXP will show the full 4GB.

Also not necessarily true - if the BIOS reports the 4GB memory address boundary as somewhere lower than 4GB, only a 64bit OS or a 32bit OS with PAE support will see most (but likely still not all) of the RAM. It has nothing to do with the OS, and everything to do with the underlying system hardware without regard to either a 32bit or 64bit processor. This issue is ENTIRELY a hardware issue - mostly BIOS, but also video RAM shadowing (we'll see more of this in Vista with higher-end cards becoming the norm) will cause RAM to not be available to the OS as well.

[Jakebo]

It is a limitation of Windows XP. I have not had a chance to look into Vista to see if it has the same kind of limitation.

[cluberti]

Vista x86 will also not see anything above 4GB - you need a higher-end server OS to use PAE on x86 (or just run x64).

[nmX.Memnoch]

But if you have a 64-bit capable processor, but 32-bit WinXP installed then WinXP will show the full 4GB.

Also not necessarily true - if the BIOS reports the 4GB memory address boundary as somewhere lower than 4GB, only a 64bit OS or a 32bit OS with PAE support will see most (but likely still not all) of the RAM. It has nothing to do with the OS, and everything to do with the underlying system hardware without regard to either a 32bit or 64bit processor. This issue is ENTIRELY a hardware issue - mostly BIOS, but also video RAM shadowing (we'll see more of this in Vista with higher-end cards becoming the norm) will cause RAM to not be available to the OS as well.

I wasn't entirely sure of that. The x64 capable machines that I've worked on that have 4GB RAM but 32-bit XP have all shown the full 4GB of RAM in System Properties. My experience with that has been pretty limited though...

[TravisO]

Well it wouldn't hurt to apply the latest bios & chipset flash to your motherboard. But I also have a 4GB setup and Task Manager only shows 3.5gb while msinfo32 does report I have 4GB.

[Antartica]

me too is the victim of the same issue... I checked it in Vista, Windows 7 but the same...I was thinking the increase the ram to 8gb but will it worth increasing...am afraid

[Tripredacus]

me too is the victim of the same issue... I checked it in Vista, Windows 7 but the same...I was thinking the increase the ram to 8gb but will it worth increasing...am afraid

Welcome to the MSFN!

If you want more than 4GB (or 3.2GB) of RAM, you need to upgrade to a 64bit version of Windows. XP, Vista and 7 32bit will only see 4GB even if you have more than that installed. Its a waste of money on RAM. Your other option is you can get the RAM now, knowing full well you can't use it, and then get a 64bit OS later.