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Nvidia 780i SLI has 2.75 Ram limit w/XP Pro

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I have a workstation with an Nvidia nForce 780i SLI MB, running on Win XP Pro 32 bit OS. The processor is an Intel Core 2Duo E6850 3.0GHz 1333FSB. It has 4GB DDR2 PC2-6400 ram. The computer only recognizes 2.75GB of ram and doesn't recognize the 3GB max that I understand Win XP Pro should see. The people who built this computer say that the MB's Bios is limiting the Ram to 2.75GB.

I wish to upgrade to Windows 7 64 bit so I can add another 4GB of ram (total 8GB) :bounce:  :bounce:  for some programs I need to use that are ram intensive. I understand that Windows 7 is not limited to recognizing 3GB of ram like XP is.

While researching the change from XP to Windows 7, the Windows 7 Advisor stated that I need 3GB of ram when using Win XP mode within Windows 7. I need to use the XP mode for some legacy software.

I've tried to find out on the Nvidia site if there is a Bios update that will utilize the full 3GB of ram. My Bios is Phoenix Award Bios v6.00PG.

Any suggestions on a work around in this matter.

More about : nvidia 780i sli ram limit pro

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Motherboard Master
Windows 7 Expert

Hi newcomer and welcome to the Tom's hardware forum.

1- What is the manufacturer of ur mobo? ASUS, Gigabyte, MSI.....
2- Win 7 32 bits has the same 3GB limitation of Win XP and Win Vista, so be sure that u upgrade the OS to x64 OS.

You have to take in account for everything on your system that has memory. 32bit operating systems are limited to 4gb of total addressable memory (including video/cache/ram.....etc). If you have 4gb of RAM installed and 32bit XP is only showing 2.75gb, then you have 1.25gb of memory elsewhere on your system.
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Motherboard Authority

That just means that about 1.25GB of memory address space, 32-bit XP only has 4GB of address space since it's without PAT, is being used by your system devices and video cards. I'm guessing you have two 512MB cards in SLI and various other devices. Thus, even though you have 3GB or RAM, windows is only able to deal with 2.75GB of it.

I only have one video card with no SLI setup and 4GB of ram which I described in my first post. I use my computer as a workstation for cad and graphics (photoshop and SketchUp).

If I understand your comments 1.25 GB of ram is being used by other resources in the system and that is why a full 3GB is not available for XP mode in Win 7. It sounds like a Bios update may not correct the problem as I have first thought. I have emailed EVGA the MB manufacturer for comment.

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Motherboard Expert

OK here is the dirty little secret when it comes to 32bit os on a nvidia based board. For each gpu installed you lose 256mb of usable ram and for the BR-04 (N200 bridge chip) that gives this board pci-e 2 spec and allow for 3x 16x pci-e slots. There isn't much that you can do with your current os except to upgrade. If you are in desperate need and use of your ram then you might as well look for a pirated copy that is clean that will do the job. XP has an annoying pop up while vista you are stuck with a black background but either than that it isn't to bad unlike an unactivated copy of Win7 which fakes a blue screen every 2 hours of use after a certain update.
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