These quad card setups have come a long way; you can really see there's some excellent scaling on offer when we compare the three and four card setups to each other at 3600 x 1920. Metro 2033 was the only game we saw the three card setup drop below the 60 FPS mark we aim for. Throwing the fourth card into the mix, though, gave us a nice little boost.
Looking through the numbers, you might find yourself wondering why bother throwing the fourth card into the mix. Well, while our in game detail is pretty much maxed out on all the games, AA and AF isn't on. Not only that, if you're on a 120Hz screen, you're going to want to be closer to 120 FPS average than 60 FPS average.
The results were really interesting, though, and it's nice to see that there's some really good scaling coming out of these expensive setups. You could see that with a single 2560 x 1600 monitor the four and three card setups had absolutely no trouble dealing with anything you throw at them. Push up to these Eyefinity resolutions and the picture begins to change; no longer are you going to be enjoying an average of 150 FPS under super intensive games like Lost Planet 2 and Aliens vs. Predator which lay such a good base line for new games that aren't as intensive as these.
If you're using a single monitor, especially a high resolution 27" or 30", going down the dual GPU path is pretty easy. Moving above that, though, is a little iffy as three and four cards while offering a boost in performance, don't do heaps in terms of having a game that wasn't playable being playable now.
If you're going to go down the multi monitor path, though, which is something that's becoming more and more common thanks to aggressive pricing on monitors, you could easily see the use for three and four card setups.
A 2560 x 1600 monitor requires a lot of GPU grunt to run; a 3x 1920 x 1200 Eyefinity / Surround Vision setup is around 70% more intensive than that single monitor. A bit like Eyefinity and Surround Vision, three and four card setups aren't for everyone. Nor are $1,000 US CPUs and $400 US Motherboards.
If you're spending the big bucks, the chances are you'll be looking at a decent multi GPU, multi monitor setup, and for good reason.