WinXP 4 GB Environment Ram Lost Due to Video Card Issue

[aoresteen]

I have a Windows XP SP3 computer with 4GB RAM using an Nvidia Gforce 9400 GT video card with 1 GB of RAM. With it installed Windows XP SP3 has 3.25GB of free ram.

With the hopes of freeing up some more RAM, I tracked down an Nvida Gforce 9400 GT card with 512mb RAM. Today I installed it and much to my dismay Windows XP reports 3.25 GB RAM - no change. What?

Both cards use the same Nvida driver. I used GPU-Z to check the physical RAM on each card. Both have the stated physical RAM on them - 1 GB & 512 MB.

Why didn't I get any gain of Windows RAM with the 512MB video card?

In any event, the heat sink on the 1 GB card blocks the adjacent PCIe slot and the 512MB card does not which was a reason why I needed to replace the 1GB card.

 

[dextermat]

Hi,

The memory on the computer (4gb) and the 512 mb ram of the VGA card are not related at all.

Windows xp is 32 bit thus limited to 3.25 gb ram. Putting more won't help.
You need to switch to a 64 bit os.

To explain this simply, the ram on the VGA is for displaying stuff on screen (youtube, word, games ect.)
While the RAM on motherboard is volatile ram (store information from programs ; spreadsheet, word text ect.) so that the computer acces it faster than other way to store volatile memory.

Hope it helps.

 

[aoresteen]

Well, they are related. Windows XP maps the video RAM into the 4gb address space and the size of the on-board Video RAM does make a difference - Windows maps what it needs to based on the size of the video RAM.

In my DAW XP system that I use for recording, I have 3.5GB of available RAM out of 4 GB. I tried about 5 different video cards in it and the one that has 128MB of ram yielded the most Windows RAM - 3.5GB; with a 1GB video card the yielded the least - 2.8GB of Windows RAM. I didn't try any card with less that 128MB as I don't have any that small that would handle dual monitors. I suspect if I put an old PCI VGA card with 32MB of RAM in I'd get more that 3.5GB. But I don't have any free PCI slots to try it.

Not only does video RAM gets mapped to the top end of the address space, so do other cards that have on-board BIOS. My SCSI card is a good example as it's BIOS gets mapped as well into the 4 GB address space.

Windows XP 32bit is NOT limited to 3.2GB in a 4GB address space. In fact by using PAE you can get way beyond 4 GB in a 32bit set up. This however requires patching the XP kernel (not supported by Microsoft) and some users have had issues doing so. I won't patch my DAW just yet but I will patch my utility XP box for testing. Google Windows XP PAE for more info.

Anyways, while I didn't expect to get a 512MB gain, I did expect *some* gain in the available Windows RAM for the lower ram on the video card.