Now before we start with the conclusion and everybody starts yelling oooy Hilbert, where are the 3-way CrossfireX results, here's the thing: I have three R5870 and three R5850 cards arranged especially for this article series to compare to. Now, we always say it ... the more GPUs you add, the more problems you can run into. Make no mistake, that rule applies to both ATI and NVIDIA. Unfortunately things for ATI became problematic. Our test system worked perfectly fine in 2-way ATI CrossfireX mode, but adding a third card would just not frickin work. It's an odd bug that we have encountered numerous times in the past already. Though the driver installation works fine and the (in this case 5850) products are recognized fine somehow ATI Catalyst decides to disable the 3rd adapter. Intriguing, puzzling, irritating yes .. but non-solvable with the limited time at hand for this article.
The only solution would have been a fresh new install of Windows 7 but that required to reinstall all games, timedemo's and test sessions all over again as well. Sorry ATI, considering even a fresh drive image made the 3rd card disable itself, we gave up as time is something limited here in the lab. We however do hope to get this working and make another multi-GPU article in the near future covering all combo's.
Okay that said, back to the product setup we are actually testing today, the GeForce GTX 470 versus 2/3-way SLI scaling. Much like the 480 we noticed that the GeForce GTX 470 scales really well in SLI mode. Especially 2-way setups work out just incredibly good.
3-way SLI will quickly run into limitations, the biggest one being your processor. Now our Core i7 965 is locked and loaded at 3.75 GHz, which already is a decent overclock. With the older or less demanding titles our setup is still not enough to feed three GTX 470 cards. We could have overclocked higher, but then the rest of our tests and results from other cards would be rendered invalid. Still, scaling was very noticeable and interesting alright.
By the way a CPU bottleneck is not so much a problem rather then a luxurious curiosity, new games will be affected by it. It does make it a little harder for us to show you 3-ways GPU scaling performance though.
Power consumption then, well it remains high .. but in 2-way SLI you can keep things under control at rather acceptable levels. 3-way SLI sucked up nearly 800 watt with the system in stress or should I say distress, 2-way SLI worked out much better at roughly 550~600 Watt, and though we do feel that this is high we also feel it is reasonable as the scaling is just tremendous.
We continue to recommend GeForce GTX 470 and 480 users to look into liquid cooling though, two 470 cards under stress produce over 55 DBa at 75cm distance from the PC, and that remains quite something.
But yea, truth is ... 3-way SLI is interesting in a geeky kind of way yet a too expensive venture, but 2-way SLI on GeForce GTX 470 actually makes a lot of sense. Money wise it certainly is a whole lot cheaper than two GTX 480 cards and the performance levels are downright magnificent. Anyway, that's it for this article, we hope you enjoyed this little read. We'll continue the SLI series soon with an update on uber extreme multi-GPU rendering, yes Quad SLI in an extreme overclocked environment, we want to shatter that personal 3DMark Vantage score of ours -- roaaar !
Personal thanks go out to Point of View and Zotac for sending out the samples in this review, you guys rock!
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