What happens with 4Gb RAM under XP?

[JPreston]

Hi All

I'm in the process of ordering up parts for a new PC and was intending to buy 4Gb RAM (2x 2Gb DDR2-6400), because RAM is cheap enough and this way I'll be ready for Vista when it eventually stops sucking.

But what happens in the meantime while I am running XP? I think XP only supports 2Gb, but does this mean that my PC will work perfectly albeit with the extra 2Gb going unused or will it give me stability problems? Will I still be getting the benefit of dual-channelness or will I just be using one stick?

[Optical668]

If you use XP32bit it will get maxed to 3GB, if you use XP64bit it will use 4GB. There seems to be no stability issues as i got 4GB and use XP32bit.

[alsenior]

it will use 4gb minus whatever the motherboard sets for the size of the 32bit memory whole. you should get at least 3.25gb unlis you have got a graphics card with a uber amount of video ram

[2Cold Scorpio]

I have 4 GBs of RAM with both 32-bit XP and Vista and it works fine; it just recognised about 3.2 GBs (I have a 512 MB video card and a dedicated sound card, etc.) of it, but i still get complete dual-channel capability with my four 1 GB sticks.

[Thorsson]

This is possibly the most asked question around.

1. It's not XP, it's any 32-bit OS.

2. Apart from the ~3.2Gb barrier, there is also a limit of 2Gb on any one program.

[Agent]

1. It's not XP, it's any 32-bit OS.

Aye, its 4Gb natively, but almost all other 32bit OS's support PAE. Even Windows 2000 (Intel Physical Addressing Extensions (PAE) in Windows 2000) which allows addressing far above 4Gb.

XP has PAE purposely locked out sadly.
Mad isn't it?

[Thorsson]

Ta for that. I have to say that it was the 2Gb limit per program that drove me to Vista64.

[dave87]

Win2k needed it cause of its server permutations which are still widely used. I don't think 2k Workstations can do the same, its just the Server variants.

[alsenior]

last time i checked xp supported PAE there i a param to pass at boot but im sure it supports it

[moogle]

last time i checked xp supported PAE there i a param to pass at boot but im sure it supports it

/3GB at the end of the boot.ini iirc

[Agent]

last time i checked xp supported PAE there i a param to pass at boot but im sure it supports it

It was removed in SP2 IIRC, but its certainly no longer supported in XP

Edit - The 36-bit address bit, just to make things clear.

[MadduckUK]

It was removed in SP2 IIRC, but its certainly no longer supported in XP

or maybe its enabled by default

[Agent]

or maybe its enabled by default

If it was, there would be no 4Gb addressing limit

[madman045]

Physical Address Extension - PAE Memory and Windows

Apparently just reading the 1st bit you can use either /PAE or /noexecute in the boot.ini file...

[306maxi]

Aye, its 4Gb natively, but almost all other 32bit OS's support PAE. Even Windows 2000 (Intel Physical Addressing Extensions (PAE) in Windows 2000) which allows addressing far above 4Gb.

XP has PAE purposely locked out sadly.
Mad isn't it?

All the PAE switch lets you do is see the RAM. The OS will still only address 4gb of ram in total and will not use any additional RAM above this although you'll be able to see it.

[dangel]

PAE is a hack - go 64bit it's the only true way to use all the memory properly. Full Stop. Period. As in THATS YER LOT.

This has been discussed soooooooo much here.