kodan50 on 7/2/2009 at 07:42
I am running Windows XP with SP3, 32-bit
I started off with my NVidia GeForce 9800 GTX installed, which has 512 megabytes of memory.
I purchased an upgraded version, the GeForce 9800 GX2, which is supposed to have 1 gigabyte of ram, 512 on each board, since this is a dual GPU board.
I upgraded my video card expecting to go from 2.80 to 2.30 gigs of RAM with the addition of another 512 megs of video memory. Instead, Windows XP still has almost the same amount of memory it did before, short by about 50 megs, even though Device Manager shows two GeForce 9800 GX2 options under Display Adapters.
In Device Manager, the "Memory Range" HEX value is used by Windows to define a usable workspace, so to speak, for Windows to do something with that device, is that right? So, for a video card to use 512 megs of RAM, the Memory Range would have a value like C0000000 - DFFFFFFF, right?
Now, if this is true, then the GX2 should have this similar kind of HEX value, but two of them, one for each of the 512 megs of video memory, is that right?
If this IS the case, here is the problem: Each of the Display Adapters has a Resource setting, but according to Device Manager, each one is using two seperate memory values of 256 each. One is in the range of D0000000 - DFFFFFFF, and the other is in the range of C0000000 - CFFFFFFF. It looks like Windows is using the same HEX range as before, but it is not allocating the rest of the memory to another HEX range.
Just to make sure I did not overlook something, here are the HEX values that each of the two Display Device items are using:
The First One:
FD000000-FDFFFFFF - 16 MegaBytes
D0000000-DFFFFFFF - 256 MegaBytes
FA000000-FBFFFFFF - 32 MegaBytes
000A0000-000BFFFF - 128 KiloBytes
Total Resources used: 304 MegaBytes
The Second One:
F9000000-F9FFFFFF - 16 MegaBytes
C0000000-CFFFFFFF - 256 MegaBytes
F6000000-F7FFFFFF - 32 MegaBytes
Total Resources Used: 304 Megabytes
For reference sake, here is the one for my GeForce GTX
FD000000-FDFFFFFF - 16 MegaBytes
C0000000-DFFFFFFF - 512 MegaBytes
FA000000-FBFFFFFF - 32 MegaBytes
000A0000-000BFFFF - 128 KiloBytes
Total Resources Used: 560 Megabytes
Well, I way over-complicated this issue, but if any of this makes any sense whatsoever, where is the other 512 megs of RAM my video card should have?
Oh yeah. I also have the latest drivers for everything I have installed. That was the first thing I checked with.
Painman on 7/2/2009 at 08:30
This is normal. The system sees the card as a 512 MB part since only that much needs any memory mapped I/O space. The last 512 is just a mirror of the first 512 so that GPU #2 can process its half of the frame, and the card has its own internal bussing and controllers to handle it all instead of getting the main PCI-E bus, etc. involved.
In case you're wondering, yes, that means the 9800 GX2 effectively is a 512 MB card, not a true 1 GB card like a GTX 280.
bikerdude on 7/2/2009 at 10:35
Quote Posted by kodan50
I upgraded my video card expecting to go from 2.80 to 2.30 gigs of RAM with the addition of another 512 megs of video memory. Instead, Windows XP still has almost the same amount of memory it did before, short by about 50 megs, even though Device Manager shows two GeForce 9800 GX2 options under Display Adapters.
Correct me if Ive missed read the question... but I think Kodan is thinking that the video card memory is added to the total amount of main memory that is available to windows..?!
Answer 1: It dosent work that way, your video card's memory is completely separate from the main memory on the motherboard. As painmain referred to its just frame memory which is only used by games, not by windows itself.
Answer 2 :Some older motherboard's do whats called shadowing and this changed the amount of available system memory.
Answer 3 :Memory mapping thats done by by the 32bit windows OS will change the allocated amount in the address map which directly changes the amount of main system memory available to Windows.
kodan50 on 7/2/2009 at 12:31
Ahh, now I see what was going on. I guess it is better this way. I wanted to use as much of these 4 gigs as I could, so this actually works out better for me. :P
Oh yeah, I wasn't expecting to use the video card's memory as system memory at all, since I was fairly certain that is a completely impossible task, unless I somehow got a program that was designed to run on the GPU by itself, which I can't be bothered to do. :P
On a side note, it works very well with Windows 7.
bikerdude on 7/2/2009 at 13:12
Quote Posted by kodan50
Ahh, now I see what was going on. I guess it is better this way. I wanted to use as much of these 4 gigs as I could, so this actually works out better for me. :P
So whats actually going on then, as the rest of us are still waiting in suspense... :cheeky:
kodan50 on 11/2/2009 at 08:02
If what Painman said was correct, then the card has 1 GB of VRAM available for what it uses the RAM for, however half of the VRAM is a 'shadow' for the second GPU. The computer doesn't see or use this shadow, so it only sees half of the VRAM. That is why I still only have 512 megs, but I have another GPU on-board to make things even more silky smoothe than before.
Did I understand that right?
EvaUnit02 on 11/2/2009 at 12:03
It's basically a SLI setup minus the drawbacks associated with SLI.
