Where is the rest of my 1.5 GB RAM!!!

Installed physical RAM of 4 GB as 2GB x 2 at dual channel interleaved but my Windows XP Professional SP3 finds only a total of 2.5 GB of RAM installed!!!

Mainboard: Gigabyte GA-P35-DQ6
RAM: Transcend aXe RAM, 2GB x 2, 1066 MHz

All BIOS settings are at recommended or automatic. Any idea?

well, this isn't entirely correct. all 32-bit operating systems will only recognize 3gb of ram...this can be either xp 32-bit or vista 32-bit. In order to recognize more than this you will have to get a 64-bit operating system. There is an XP 64-bit and a vista 64-bit (more common).

Hmmmm not sure about that. Windows XP only recognizes 3gb, but your system BIOS will recognize the entire 4gb. So does this mean programs will recognize 4gb even though Windows does not.....not sure about that

Can anyone else confirm Windows VISTA can surely utilize RAM for 4GB or more? I guess, if Windows VISTA can see 4GB or more, Windows 7 will be be the deal

Ok, at this point, can someone tell me which one of the following will be faster for 2GB RAM @ 1066 MHz?

a. 1GB x 2

b. 2GB x 1

Thanks to RedDragon & Smartel.

Can you tell me if Intel X58 chipset with Intel Core i7 supports this memory swapping feature to utilize 4GB or more RAM (of course in association with an OS of 64 bit, perhaps 128 bit or more )?

Keep your 2x2. Buy a better video card with 512MB of RAM and you will gain 0.5GB of system RAM.

All modern chipsets support memory mapping techniques to allow larger-than-4GB capacities under 64-bit operating systems.

Vista 32 bit SP1 cannot use 4 gig of memory. It displays that there is 4 gig of memory installed like the BIOS does and all of it is not available to the OS or applications. It has the above mentioned limitations of a 32 bit address space.

That doesn't make it more useful though. It is simply to placate users who want to see their full 4GB.

theAnimal & FlorinR,

Yes I do have a PCI Express graphics card with 1 GB DDR II onboard VRAM, that is nVIDIA XFX 8600 GT.

that is why you can only see 2gig in the XP main menu.

32bit XP can only address a total of 3gig period. no way around it. so because your video ram cannot be dissabled by windows it will disable the other 2 DDR2 sticks. so your PC is actually addressing a full 3 gig.

upgrade to a 64bit OS and let your system stretch it legs.

There is really no point in a 1GB 8600GT. You'd have a much faster machine with something like a 9800GT or 4830 with 512 MB of RAM, and you'd see 512 MB more of your system RAM (bumping it up to 3GB). Alternatively, you could just drop the $100 for an OEM copy of Vista Home Premium x64.

Guys:

a 32 bit OS can only address 4GB of address space (2^32 bytes). Any device that needs to be used will take up some of that space (motherboard, sound cards, GFX card, etc).

After basic computer components, about 256k or so is already used up. Subtract any RAM installed an a device (sound card or graphics card) from 3.75GB, and that (in theory) should be your maximum amount of usable RAM. And as most GFX cards are 512MB, thats where the 3.25GB limit comes from (which is incorrect, as a card with less RAM would lead to more avaliable main memory).

The only cure is to move to a 64-bit OS. End discussion.

yes, newegg sells oem vista 64 premium sp1 for $100. i have 8gig ram and can use all of it in vista 64. i dual-boot to xp pro sp3 32-bit and it only sees 3.25gig ram. i almost never boot into xp. i use vista for everything and works great.

Not nessacerily. The 1:1 mapping usually don't apply when VRAM (per GPU) goes beyond 256MB.