If you take a look into the past, multi card setups have always been a somewhat temperamental solution to the never-ending quest for high performance. We remember a time when just getting SLI and Crossfire to run properly in the vast majority of applications was a lesson in frustration. Well, times have changed. While scaling still isnít perfect across every game for a number of reasons, both NVIDIAís and ATIís technologies have matured to the point where we can consider them a viable option for people who want the best of the best. Naturally, there are still pitfalls as we saw with NVIDIAís rendering problems in Aliens versus Predator (EDIT: Please note this is a game issue that affects NVIDIA cards and NOT a driver issue. It should be fixed in an upcoming patch.) ) and ATIís image quality issues in Battlefield: Bad Company 2 but these scenarios are much less prevalent than they were about a year ago. That in itself bodes well for multi card setups.
Back when we first reviewed the GTX 470, we were impressed with its overall performance in comparison to the HD 5850 particularly when image quality settings were increased. Our observations regarding a framerate advantage havenít changed when another card is added since for the most part two GTX 470s in SLI still routinely beat out a pair of HD 5850 cards.
However, the facts are quite clear: in general, ATIís cards offer better multi GPU scaling than anything NVIDIA can currently offer. Believe it or not, NVIDIAís SLI scaling is actually very, very good considering we saw on average a 60% to 81% increase when going from one card to two. Weíre just not that excited about it because ATI threw a live hand grenade into the SLI party by posting performance increases that were simply jaw-dropping in nearly every respect. It is because of this dual card scaling that a HD 5850 Crossfire setup can make up a ton of lost ground when compared to ATIís single GPU scores. On the other hand, the HD 5970 is simply trampled by the GTX 470 SLI setup.
Luckily for NVIDIA, we didnít stop at the average framerates and included (as usual) minimums as well. In this category the GTX 470 SLI is still head and shoulders above the competition when IQ settings are pushed since it doesnít exhibit the numerous dips in performance that characterize the Crossfire experience. I donít know about you but I would much rather have a slightly lower average framerates if it means my system wonít bog down when Iím fighting for my life in a game. Basically, a fluid gaming experience is what SLI is ideal forÖor at least until ATI can figure out a way to bring up their minimum framerates in some games.
Considering the drivers we were using for NVIDIAís cards arenít exactly what we would call mature, the stability these two GTX 470s exhibited was nothing short of praise-worthy. There was a minor hiccup when it came to rendering some overhead objects in AvP without AA enabled but other than that, sailing was smooth. ATIís solution on the other hand had numerous issues in Aliens versus Predator, Metro 2033 and Battlefield: Bad Company 2, only of which the latter didnít affect gameplay too much. There were also problems with the drivers (10.3a and 10.2 WHQL) actually detecting both cards which seems to be a reoccurring frustration with every second driver from ATIís team. NVIDIAís average SLI scaling might not be up to the level of Crossfire but its seamless implementation has yet to be equaled by the competition.
While performance is good and minimum framerates are awe-inspiring, our main concerns about a GTX 470 SLI lie in two areas: price and power consumption. Both aspects wouldnít have been too much of a concern if NVIDIA had managed to carry their average single card performance lead over the HD 5850 into multi card benchmarks. Unfortunately, that didnít happen so as it stands we feel that spending $700 for two GTX 470 cards is a hard sell when you can buy a similarly performing solution from ATI for more than $100 less. When you add a power consumption gap of more than 100 watts into the equation, it becomes extremely hard to recommend a GTX 470 SLI setup at this point in time for someone who isnít hell-bent on going with NVIDIA cards.
It is quite evident that while the GTX 470 is a clear winner against a single HD 5850, SLI is currently struggling to mirror the downright amazing scaling that Crossfire offers. Overall framerates for a GTX 470 SLI system are still incredible but the HD 5850 in Crossfire is simply too close for comfort in most cases. It is also important to remember that NVIDIAís drives are still quite immature and multi card performance is usually one of the first things addressed when new versions are released. As such we intend to take another look at GTX 470 SLI performance in the future. While we canít outright recommend going SLI in this case, it offers enough convincing performance wins that it should be at least considered by enthusiasts.
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