I'll try to do this fast.

I have a dual-boot system (P5B-Deluxe, 4*1GB DDR2-800 memory, E6600 @ 3.0ghz rock stable, Asus X1950Pro) with both WXP Home 32 bit AND Vista Home Premium 64 bit. I enabled memory remap feature in my BIOS so I could use my whole 4GB memory under Vista.

The problem is that I now see "only" 2GB when working with XP. It's really not the end of the world, but is there a way to change this?

I know there is something you can change in the boot.ini to make Intel (AMD also maybe, not sure) cpu see more then 4GB of memory when in a 32-bit Microsoft OS, in my case up to 6GB (2GB memory, then 2GB reserved for drivers and finally 2GB remapped). It's only that I don't want to play with XP boot.ini if that might prevent me from going into Vista.

I looked around with google but found nothing. Anybody has a link for me of some quick explainations?

Thanks in advance for any help.

NS, I'm no expert on this but I have the same rig you have, except for the video card. With 4 gig installed enabling memory remap will drop you down to 2 gig in 32 bit and I do not think there is any way around this. At least none that I could find after some serious Googling.

And yes, unless you enable memory remapping you cannot get your full 4 gig in your 64 bit Vista.

For what it's worth I do not think there is any way to really use 4 gig in a 32 bit os. The 32 bit OS can only ADDRESS 4 gig. That's the limit. And since other devices aside from your system RAM have addressable memory the OS must reserve some addressing for those devices thus reducing you down to about 3 gig+/- useable system RAM.

IIRC there is a fix, PAE, I think it's called, for getting some 32 bit apps to use a larger chunk of memory than they are usually allotted but this is only for server OS and some special apps such as SQL server. But I'm a little foggy on that.

It's pretty much a done deal that with 32 bit you have to live with what you get - about 3 gig+/-.

If there is a way to leave remapping enabled and get the 3 gig seen in 32 bit I'd love to hear about it. I could find no fix for that.



I suppose leaving remapping enabled might be the best bet for us since XP doesn't really need more than 2 gig RAM, from what I have heard anyway.

nd is right: you need remapping to go to 4GB or more with a 64-bit OS, but you need remapping off for a 32-bit OS.

It would be a couple of extra steps each time you reboot to a different OS but, you could manually change it in the bios. Also, does that MOBO save bios profiles? If so, you could save one of each and have them available when you boot each time and choose the option that fits the OS you are going to run.

It's PAE that I had in mind, but I guess it'll be quite difficult (if possible) to get it to work under WXP Home Edition.

Like notherdude says, it's better to have XP at 2 GB then both Vista and XP at 3GB without remapping. Anyway, XP is there only for older application that won't run under Vista 64 bit.

Thanks all of you.

Microsoft has essentially disabled PAE use for increased memory under the consumer versions of Windows. It can only be used to enable the execute-disable (XD) functionality.

Agreeance with Mondoman the PAE switch is useless under XP.

I have the same mobo with 4gb ram and XP 32Bit, if i do not enable remap the BIOS only detects 3.***GB and windows uses this. With it Enabled i get 4Gb in the BIOS and 2Gb in windows. I dont know if this has changed with new BIOS Rev. though.

Id suggest setting up a BIOS profile for vista and XP changing this option to suit the OS of choice. In any case XP is never going to use all your 4Gb infact it will only ever use around 3Gb.

I'll try updating my BIOS to the last one (I think I'm still at 604 or something like that ).

If that doesn't work, I'll just do dual-bios setting depending on which OS I plan on starting.

Thanks all.