Waffles in Thirty Seconds or LessThe Tech Report has an interesting article on Nvidia SLI today:
I hadn't previously mentioned heat as a potential problem with these systems because the first batch of articles barely even mentioned it as a factor. However, logic would dictate that when two high-powered cards are put in the same system, heat is going to cause problems.
The new set of reviews coming out (mostly in the last 5-7 days) seem to bear this out. Every review mentions the test system crashing on a regular basis, and the linked article mentions that heat seems to be the primary cause.
That should be no surprise when you look at some of the test results in the article. Scott Wasson measured power consumption in the test systems at idle and under load. Look at this:
GeForce 6800 Ultra SLI--223 idle, 365 under load.
GeForce 6800 GT SLI--223 idle, 361 under load.
GeForce 6800 Ultra--155 idle, 271 under load.
Geforce 6800 GT--153 idle, 257 under load.
Radeon X800 XT-PE--115 idle, 219 under load.
Radeon X800--110 idle, 193 under load.
Please note that this is total system load, not just graphics card power consumption, but if you look at the test specs, you'll see that the systems were relatively bare.
If a system can reliably dissipate 365 watts of heat, it's going to be so packed with fans that it will be loud. Very, very loud.
Here's the other problem besides heat. If you remember the last time I mentioned SLI, I talked about how different games would use different optimization techniques, because the SLI method was going to be configured by game. I should have realized, but didn't, that this meant every game would be a custom addition to the drivers, or at least it appears to be that way. So this is not really 'plug and play' where you get automatic SLI support for any game that supports D3D, for example. It makes it possible to have higher levels of optimizations for benchmarks and a few high-profile games, but I'd much prefer broader support, even at the cost of some performance.
The other interesting note in the article had to do with Radeon X800 XT-PE performance. In some games, it actually outperformed an SLI setup with two GeForce 6800 Ultras--with about 150 fewer watts of power consumption. So if ATI has some kind of SLI solution next year, as they claim, two X800 XT-PE's would provide pretty astonishing levels of performance.