Nvidia 780I motherboard and Ram

[na8ty78]

Hello I just swithed back to xp form vista 64bit. It was not running as smoothley as I would have liked. Here's my question... I have the Nvidia 780I motherboard I have 8gigs of DDR2 800Mhz of ram, now I know xp pro 32bit can only use 4GB. Now they are 2GB sticks, but for some reason I only see 2.25 in my computer propertise? Do I need to buy 4 1GB sticks in order to get 4GB?

THANKS!!!

 

[Mondoman]

No, it's just that your installed hardware (probably graphics card(s) with lots of onboard graphics memory) have used up a fair bit of that 4GB maximum. 2.25GB is a reasonable amount to be left over for Windows use if you've got big graphics cards.

 

[na8ty78]

I have 2 8800 GTS 512 video cards running SLI, why would it need more?

 

[Mondoman]

What does "it" refer to?

 

[na8ty78]

not sure what you mean

 

[Mondoman]

You ask "...why would IT need more?" What does the word IT refer to in that sentence? What is it that needs more?

 

[na8ty78]

You said my video card is taking some of my ram. Why would it do that if its already got around 1GB 512x2 SLI

 

[na8ty78]

I have a total of 8gigs installed atm

 

[na8ty78]

I just removed 1 and now I have 6

 

[Mondoman]

No, I said your video cards are taking up some of the 32-bit mode's total of 4GB of *addresses*. RAM without an address is invisible to the system. When you boot up the system, before the BIOS kicks in, 4GB of addresses are available. The BIOS takes some of those addresses and assigns them to various system hardware. Normally, this doesn't make a big difference, but because a graphics card is assigned enough addresses for its onboard RAM and then some, you're using up maybe 600 or 700MB of addresses per card. With two cards, that uses up something like 1.4GB of addresses. When you add in the other addresses used by the "normal" system hardware, you've used up another few hundred MB of addresses and you're down to only 2.25GB of unused addresses. It's only at this point that the BIOS assigns addresses to the main RAM. Sure you've got 8GB of RAM, but since only 2.25GB of addresses are left, only 2.25GB of RAM gets addresses and is visible/usable by Windows.

 

[na8ty78]

Is there anyway to free up addresses?

 

[Mondoman]

Remove one or both video cards or replace them with video cards with less onboard RAM.
Of course, that will reduce your graphics performance, so if you want to keep that, don't worry about the RAM.