I'm running a triple monitor setup for productivity purposes. I'd like to give surround gaming a whirl. This is a relatively simple/stupid question but I don't know how SLI actually uses the GPU's memory. I'm looking to pick up a single 680 and SLI later down the road. So, does SLI utilize the memory of both cards, or just one? i.e. does 2+2=4 or does 2+2=2?
I'd like to think that 4GB between two cards would be more than enough for good frame rates on a 5760x1080 setup, but I'd rather buy the right cards in the first place. If I should wait for the FTW edition, so be it.
SLI Memory bandwidth works like this, What ever monitor that card is hooked to is the amount of memory that monitor has. When you have two plugged to one card, it shares the memory so probably around 1GB to each monitor. when you have 2 cards and 3 monitors... Well same concept and theory just more memory to go around. But for example if i was to plugg 1 monitor up to one of the Two GTX 680's you'd only have 2GB of vram total because Vram doesn't pool between cards, it spreads between monitors
I dont understand Rockdpms explanation at all, I'm not saying its wrong I just don't understand it.
The way I was taught was this.
Both cards are at 2GB of vram, the problem is both cards have to load all the information that is necessary, if one card must load this texture, then so much the other. Thus you technically do have 4GB of ram, the problem is each card is loading the same information at the same time, thus you only have 2GB of effective memory.
don't worry about that monitor explanation, and spanning monitors. this is how it works; it doesn't matter if you have one monitor, two monitors, or three monitors, you will have 4gb of vram but only 2gb of effective ram. it is effective ram because all data going into the first card must also go into the second card to be processed by the second gpu as well. so you really only have 2gb to work with.