Does SLI combine memory?

Hey ok im just wondering if somebody can explain SLI, im not sure if it combines memory or not, and if it doesnt explain how. thanks!

Yes and no.

It is a similar methodology 3dfx used in their 64MB Voodoo 5 series, where each VSA-100 chip had 32MB of memory on a dedicated bus.

Textures and geometry data are duplicated between the two cards, because each card has to have access to the same textures. Thus, SLI will probably not allow you to use, say, Doom 3's "ultra" texture mode (best on 512MB cards) with two 256MB cards.

The framebuffer, on the other hand, is independent between the two cards. You get double the framebuffer bandwidth over a single card, and double the framebuffer space, which is why you can turn up the resolution and AF / AA with high performance benefit on SLI.

So yes, you get somewhat better memory bandwidth, and you get improved performance in terms of memory for framebuffer, AF or AA. But texture performance will not improve much.

No, it does not. Neither does Crossfire.