Vista - Missing RAM with SLI enabled

Hallo all..looking for a fix...if possible....if no fix, then at least an explanation..the hows and whys...

I have Vista 32 Ultimate with SP1.
Here are the rest of my system specs:
XFX 780i motherboard--shipped with P02 bios, already updated to P04, which was just released
Intel Quad Core Q6600 2.4ghz
4GB G.SKILL 240-Pin DDR2 SDRAM 800 PC2 6400
2 XFX GeForce 8800 GT 512MB PCIe 2.0--SLI'd
Creative Soundblaster X-Fi Xtreme Gamer PCI
WD Raptor 74GB
Seagate 250GB
D-Link DWL-AG530 32-bit PCI Wireless Adapter
2 Pioneer 20X DVD±R DVD Burner Black IDE Model DVR-115DBK

Yes the bios recognizes all 4GB AND the "My Computer" UI "displays" 4GB.

I know, though, about the 3GB limit of a 32bit system(I hear people say that Vista 32 utilizes (NOT recognize, but UTILIZE) 4GB of RAM, but I have yet to see any evidence that supports that, so I will stick to the idea that 3GB is the limit)

I know that the 3GB=System RAM+Video RAM.

I install 1 Nvdia 8800GT 512mb video card.
System RAM reads 2.5GB. 3GB of System RAM-the 512 of the video card=2.5GB. goody gumdrops.



I insall the 2nd Nvidia 8800GT 512 video card and enable SLI.
System RAM reads 1.5GB?



Shouldn't it read 2.0GB?? 3GB of System RAM-512 for card 1-512 for card 2=2.0...not 1.5...???

Where did the missing 500mb go?

AND IF Vista 32 is supposed to be able to utilize 4GB, then shouldn't my RAM read 3.5 before SLI and 3.0 after SLI???

I have built and rebuilt, installed and reinstalled and I still come up with the same thing no matter what I try.

I would love a fix...if not, an explanation as to the hows and whys of what is going on...I would at least just like to understand.

Thanx all!!

sorry if this double posts I got a error when posting.
32bit OS's can only map 4gb of memory. This includes RAM + video ram, plus
some system addresses. So your shown windows ram is probably a little less
then 4gb minus video ram.

"legend0fthefall" wrote:

check for a remapping feature in your bios

"legend0fthefall" wrote:

With the BIOS reserving memory for memory-mapped IO for your two 512mb video
cards and some other devices I am not surprised that you are showing 2.5GB
available for user programs. That is about right. My systems range from
2.2GB to 3.5GB. The 3GB number you cite is largely fictional since the
range across various machines is quite wide. I have seen the most
frequently cited number here at around 3.2GB. Your math result of
subtracting 512mb from 3GB is irrelevant since 3GB is not a Windows
limitation but just a commonly cited number for the user space. The mobo
manufacturer plays the major role in what is hidden from the user under
32bit Windows.

"legend0fthefall" <legend0fthefall.37oa87@xxxxxx-mx.forums.net> wrote in message
news:legend0fthefall.37oa87@xxxxxx-mx.forums.net...

[/quote]

Thanx for the answer!!

But still, under that reasoning....I don't have 2.5 GB of video ram, I have 1 GB

So I should be showing 2.7-3.2 GB NOT 1.5....

[/quote]

Hmmm

I took a trip through my bios a few hours ago...

I am a little wet under the collar when it comes to fiddling with the bios...

What precisely might I be looking for??

That 2.5 is with 1 video card though...

How in the world would adding another video card drop it another gig??

If Vista really does utilize 4GB, wouldn't my physical memory read 2.7-3.2 GB?? Instead it is reading 1.5gb.

I have 1GB of video memory, not 2.5GB. That is A LOT of missing memory..

You know that you can check it yourself, don't you? Go into the Windows
Control Panel's Device Manager and see what memory addresses are being
used by each hardware device. For example, on the machine that I am
typing from, the nVidia 7950 GX2 (single card, dual GPU) shows memory
address usage at:

000A0000-000BFFFF
B0000000-BFFFFFFF
C0000000-CFFFFFFF
DB000000-DEFFFFFF

The last hex number(DEFFFFFF)is approximately @ 3.7 GB decimal. There
are a bunch of other devices using memory addresses and some of them
also may be related to the video card. Keep in mind that every video
card might be implemented differently. I sure that someone has written a
piece of software that will display a graphical map of the entire
address space for a specific machine. Here's a generic explanation:

http://www.codinghorror.com/blog/archives/000811.html

legend0fthefall wrote:

I have 3.5GB available on one of my computers running Vista Ultimate x86.
Obviously it varies according to the hardware. I suggest you check with the
mobo manufacturer about what is going on with the machine. In any case,
there is no automatic 1GB deduction nor is there an arbitrary ceiling at 3GB
for the user space. You just have to look at the specific computer to see
what is being mapped out.

"legend0fthefall" <legend0fthefall.37olc3@xxxxxx-mx.forums.net> wrote in message
news:legend0fthefall.37olc3@xxxxxx-mx.forums.net...

>
If you need, or just want, to use all your RAM the solution is to switch to
a 64 bit OS. Yes, that may introduce other problems but it is the only way
to use 4 GB or more of RAM with Windows.

--
Kerry Brown
MS-MVP - Windows Desktop Experience: Systems Administration
http://www.vistahelp.ca/phpBB2/