View Full Version : Using Extra Memory

Mr Bigman
11-04-07, 04:16 PM
Why couldn't SLI use ram off the second card?

This make good sence since SLI is for using 2 cards to perform the duties of 1 game.

This help alot wouldn't it for those who have 256mb cards so they get 512 framebuffers off the 2 cards.

11-04-07, 04:38 PM
both GPUs need access to the same scene data, textures geometry and stuff.
So you would need to link the memory for that to work, which would require a VERY fast link to not bottleneck everything severely.
Preferably as fast as the bus from GPU -> onbard memory.
And I dont think that is possible over that distance, or atleast not cost effective.

Its not like it only uses the RAM off one card, but it needs to keep the same set of data on both cards, so it uses the RAM on both.

Mr. Nice
11-04-07, 04:38 PM
It already does use the memory of both cards. However, I assume you are referring to the fact that textures are duplicated between the two cards? This is neeccessary from a performance standpoint since even with the SLI bridge, there just isn't the bandwidth between the cards to lookup textures being held on the other, without exactly the same kind of performance hit you get when they have to lookup textures in system memory.

Mr Bigman
11-05-07, 12:04 PM
So your still getting the performance from both cards equaly but it duplicates the scenes so both cards work on the scene?

Thats not bad.

I thoought they could go slip screen and have one card render on half and the other render the other half.

I thought thats what was done in the FarCry demo bach when it was tested on Alienware pc's.