Quote Originally Posted by Behemot View Post
The memory is hidden from OS or what? If it is not and OS is able see it, it has to cut some RAM as well as some VRAM since the system needs something to run. Usually it cuts the RAM first, but it probably just cannot adress 4GB VRAM and 0 GB RAM because it won't even start.

The x86-32 systems simply adresses up to 4GB and the rest is unavailable and could not be used as long as it is not hidden from the OS somehow. Or at least this is what I saw every time with 256 or 512MB cards. But I personally did not have card with higher amount of memory in hands
I dont think the OS counts the VRAM that way. If you use some of the main ram for a igp say a 3200 it is not seen by the OS the same way hence the RAM size shrinks.

EG If you have 4GB ram and you assign 1GB to your igp the OS does not see that 1GB in the same way as it will see the other 3GB's...

For CF's/SLi if the OS kills ram in any of the system it will be a huge penalty because both basically copy each others vram and will be in a pickle if either vram or main ram is decreased in size..