When review motherboards, all I see is a single GPU at x16; 2 at x8 x8. Are there 1150 boards that support x16 x16 for SLI, or is that a pipe dream?
In Intel's case, because the primary PCI-Express controller is in the processor package and at the moment, Haswell only supports 16 PCI-Express lanes for graphics, it's a pipe dream to get full 16 lanes per card. Motherboard makers can get three-way or four-way SLI by using a customized chipset that allows for more PCI-Express lanes, but as you may know, these run in the $250+ category. However, there's no problem here as even the GTX 680 is does not see significant performance losses until you put it in a PCI-Express 1.1 x8/PCI-Express 2.0 x4 slot. Are there performance losses at higher speeds? Sure, but not enough to care about unless you're itching for the fastest benchmark scores.
And for the sauce: http://www.techpowerup.com/reviews/Inte ... s_Scaling/
Since I've never done it, is SLI something you have to switch on/off depending on your intent? For example, if I'm just surfing the web do I have to turn off SLI and when I'm ready to game I turn it on?
SLI is always on, but the other graphics card just goes to a lower power state if it's not being used.
So anyway, I'm going to throw things off here and offer my two cents after using a multi-graphics card setup for a year and a half. After doing it, I won't do it again for several reasons:
- Given that I only game on one 1920x1200 monitor and even modern midrange graphics cards can run games at maximum settings at 60FPS (or at least "smooth"), there's no point in getting more performance than necessary. I should only get what I think will last me for a while (two years, give or take).
- I'd only consider multi-card setups if they have a good price/performance ratio over what's better to it currently. In my case, I bought two GTX 560 Ti's because they were better than a GTX 580 and cost less.
- Multi-card setups obviously chew through more power both idling and under a load, but this may or may not be a concern. There's also the issue with temperature.
- One problem I also find is that it's harder to get rid of two cards than one, unless you happen to know people who are willing to take your obsolete hardware... But that might not be too hard for those who think PC gaming is expensive and want in on the action.
- I've also noticed there are subtleties too. For instance, I took out the GTX 560 Ti's and put in a GTX 670. I noticed in some games, notably Skyrim, it stopped stuttering, even though both setups are more or less equal in performance (maybe more VRAM in the GTX 670 stopped a bunch of texture swapping or something?)
- And another heavy hitting reason: say I bought two $300 cards for performance... Except I could spend $400 on a decent card, pocket the $200, and within a year or so when the next big thing comes out, upgrade to something that would perform about the same or faster as the $600 setup for the same price if not less.
But it's up to you. To me this is really a game of patience and gambling.