What happens when load is too high for the PSU?

[Actaeon]

I've got a quality PSU, a Corsair AX850 but a recent GPU upgrade is really pushing the wattage required. Reviews of this setup seem to be pretty close to the 850W at times. Not sure if they're measuring from the wall or output, but either way its pretty close to the limit.

I am curious to know what to expect if I go over the rated load. I expect this to happen when I'm playing a game. Does the whole computer freeze? Does the application close? Will it just shut off? Will it reboot? Will it blow up?

Thanks.

 

[smitbret]

General Instability, BSOD, System will Reset when you put it under load like loading something graphically intensive

Oh, and a burning smell.

 

[zir_blazer]

Any decent Power Supply should trigger an overload protection and shut down. It may hurt life expectancy if you have it doing heavy duty work at the limits through even if it works properly.
If in doubt, try to look around if you can do some undervolt and/or underclock. Depending on the performance levels you need, you may save some serious power consumption and not lose too much performance.

 

[Actaeon]

Okay, thank you. I think my unit can handle the stock clocks/voltages. Reviews I've seen shows a similar setup pulling in around 650W, so I have plenty of room to spare there. My system does run a bit lean (a single 2.5" HDD used for laptops, no opticals).

I've been playing around with overclocks and it seems to run 3D Mark FireStrike back to back to back no problem. No artifacts, no stability issues, no throttling or anything.

But when I load up a game, stability is questionable. Sometimes the game runs fine, sometimes it crashes in 30 minutes, sometimes it crashes just a few minutes into it. Doesn't crash or lock up the computer. Only the game. I can go ahead and start the game back up again.

Trying to figure out if its a power issue or if the overclock is just unstable. I was playing around with different settings to see if is the memory or core, but I didn't have time to finish my testing to draw any conclusions before I had to leave. I will continue testing when I get back home. I brought the core and memory down quite a bit from where I was able to complete many back to back 3D Mark runs but the game still crashed. This is what is making me think its a power issue. Maybe the game draws more power than 3D Mark. Lower clocks seemed to help increase the MTBF but perhaps that was because it needed less power, not because the clocks were too high.

I guess I need to find a balance between getting higher clocks and keeping power in check. My PSU is good quality and not very old, so I would feel wasteful buying another for this reason alone. But I do want to get as much performance as I can from what I have.

Thanks again.

 

[Actaeon]

In case anyone was interested, I did some more testing. The conclusive test was stock clocks but still overvolted. Game still crashed. Don't think it was a heat issue. Must be power.

Dropped the volts and now running a mild overclock and its been pretty steady so far. Still testing but I think I found the root cause.

EDIT: Nevermind, it crashes even on stock settings and stock voltages. I think the game is just buggy. Everything else seems to run fine.

 

[VirtualLarry]

Generally, a quality PSU will shut down if overloaded. Crappy PSUs can burn up, or just get really unstable. I suppose it might be possible for a quality PSU to not deliver stable power either, but generally they are engineered to either run in spec, or shut down.

 

[Flapdrol1337]

An AX850 will shut down if the load is too high.

Anyway, what are your specs? Some people really overestimate powerconsumption.

 

[Actaeon]

Thanks for the info. I haven't had any shut downs only the app crashing. I think its an application issue, not an issue with the power or OC as I think about it more. It is only that one game which has known stability issues (had to Google it). Applied a 'fix' the other night but was too busy this weekend to confirm it, will test it more today.

Computer specs are

Intel Core i7 2600K OCed to 4.5GHZ (minor overvolt to 1.2v-ish)
Asus Sabertooth P67 Motherboard
16GB of RAM (4GB x 4dimms)
2x AMD Radeon R9-290X (these are the hungry power monsters)
Corsair AX850

I was guessing it was power since a pair of OC'd 290Xs bring it pretty close to 850W. These are the tests from HardOCP. I don't have the XFX versions but close enough.

Tweaktown got even higher numbers... these sound crazy and way higher than anything else I've seen though.