Originally Posted by Votkrath
What are the risks of having not enough wattage? I have never had a chance to even consider something like this since I've never run SLI but a friend is and we are curious about what kind of PSU will be needed for:
MSI 980 Ti gaming x2
3 HDDs (m.2 ssd, normal ssd and a mechanical)
He currently has a Corsair AX860, non i edition. It is borderline but other than paper efficiency, is there any possible hazards or damages to the components?
I remember back in the day of the 6600 GT that when I put it into an old Dell computer that I got an nvidia popup every now and then saying it is decreasing it's performance because it doesn't get enough power.
The computer will have very high uptime but would it be possible to use the AX860 for now until next month or so?
When you have a high-end PSU like that, you can pull more than its advertised capacity out of it because its advertised capacity is just its continuous capacity. That means that this PSU can deliver 860W 24/7 if it's ever needed and could deliver a lot more than that (maybe 50-150W more) for brief moments. If you go above its absolute peak capacity though, a high-end PSU like this would just harmlessly turn off. A low-quality PSU though could kill your system if you're not careful. It's not a highly-likely thing, but it would still be possible. So, it's a good thing that this system is being powered by a high-end PSU.
Anyway, having said that, he has enough power unless the CPU is overclocked to extreme extremes - if that makes any sense. You are right that two 980 Ti's at stock can pull about 500W out of the PSU all by themselves. If you overclock the 5930K high enough, then it could pull over 350W all on its own. So, in such a situation, a potential could exist of riding about 800-850W while gaming. Overclock the 980 Ti's yourself and then you're looking at needing more power. Having said that though, it would be harmless to pull more than the AX860 is capable of delivering because again, it would just turn off (it's a safety feature). He wouldn't run into any problems at all. Amusingly, that's a bad thing because he wouldn't have any warning that the power consumption is getting close to causing the AX860 to turn off.
So really, as long as he doesn't overclock the 980 Ti's himself (as long as he leaves them at the stock factory overclock), the AX860 could keep powering this system "forever".
Edited by TwoCables - 10/30/15 at 6:53pm