Depends on how much system ram he has surely?
Either way, its a pointless argument. He needs 64 bit windows for it to work correctly.
This is why I said it's complicated. It seems I lied when I said I was only going to mention this once, and now we've gone off track from the question. If the OP could put up working links again that would be awesome. According to you Rob he should have ZERO ram. 32bit windows can only address 4GBs of space, and that 4GB card would take up
100% of the address space if things worked the way you think it does. But the reported problem wasn't "I have no ram", but "DX report tool says I have a 680MB GPU" That's a bug in the report tool, not a 32bit address space issue.
He needs 64 bit windows for it to work correctly.
Again, it's working for the OP but he's seeing numbers he's not sure of. It DOES work. Let me try another example.
https://blogs.technet.microsoft.com/markrussinovich/2008/07/21/pushing-the-limits-of-windows-physical-memory/
I purchased one from a boutique gaming rig company that came with 4GB of RAM and two 1GB video cards. I hadn’t specified the OS version and assumed that they’d put 64-bit Vista on it, but it came with the 32-bit version and as a result only 2.2GB of the memory was accessible by Windows.
According to the way you think, he should have <2GBs usable. Two 1GB GPUs needing 1GB each, plus more for the other system devices. Yet he has 2.2GB usable!
Device Manager reveals that 512MB of the over 2GB hole is for the video cards (256MB each)
Again, as I said in my first post, not all of the Vram is mapped in windows. Cards need lots of Vram to do things like AA and other post processing effects. Windows couldn't care less about such things. It does need to map some space so it can run the GPU, but it doesn't map on a 1:1 basis. And because we are messing up the OP thread I'm moving on from this discussion. We are so going off topic.
OP, you said GPUZ reports 4GB, I'd trust it over the DX report tool.
Edited to fix a quote.