power supply - Can PSU cause my PC to reboot?

I'm having an issue with my PC: It is rebooting sometimes, and I am suspecting the PSU, so I want to confirm a few things. It is a new PC and the first issues started occuring roughly one month after purchase. Also they only occur after several hours of usage. And it seemed that completely shutting down powerline to the PC, and waiting few minutes, then putting it on again, seemed to relief the issue, but that might be just coincidence?

First off:

• Does the PSU capacity decrease over lifetime of the PSU?
• Does the PSU capacity temporarily decrease as it is active for a continious time?

My PC specs: Intel i7-3770, 16GB RAM, GTX 770, SSD, HDD. I think Asus Z77 motherboard.

As you can see it is pretty high-end, but I rechecked the PSU on the invoice yesterday and to my surprise I found a 30 euro PSU, namely the HKC V-550.

My system draws 480W of power from the powerline, if on full GPU & CPU stresstest. This is a heavily modified version of their base system, which did not include such a high-end GPU as the GTX770.

Also, as far as I know, a system shutdown (without! bluescreen) can only occur, if:

• PSU shuts down
• CPU shuts down
• Motherboard shuts down?

But to me it occurs to be logical that the PC would not reboot if the CPU or Motherboard had shutdown, yet with a PSU and a safety switch it might seem logical that it could reboot.

Also about the reboot: The PC "on"-LED in the front turns off once it reboots, and in my headset (that is connected through USB) I heard some kind of clicking sound once when it turns off, and once when it turns on. Might that be enough reason to believe that it is the PSU?

Also, the temperatures of my CPU and GPU, actually of my whole PC, are perfectly fine under load. The only real test I have not been able to do yet is Memtest86, but wouldn't that lead to a bluescreen under windows anyway? Instead of a reboot.

Well I hope someone is able to help me here.

To those who feel like commenting on this answer or even downvoting, please make sure to read it in full and check out the links before you do so. Constructive criticism is by all means welcome, but I don't fancy fielding comments that are already covered by the answer itself. Thank you.

It seems like your current power supply is underrated for the load you are putting on it. As you found, the PSU can provide a maximum of 24 A on the single 12 V rail (288 W), while the GTX 770 supposedly (according to the OP's comment) needs 42 A at 12 V (504 W); @davidgo found a TDP of 230 W for the GPU itself, which goes well with figures published on Tom's Hardware saying about 250 W is needed. The graphics card drawing "just" 250 W would still leave very little margin for anything else on 12 V when the graphics card is working hard. Things that run on 12 V are usually those with motors: spinning-rust hard disks (clocking at about 10 W apiece when working, more on startup), fans, and (as you have found out) some high-powered electronics. To prevent worse problems, including short circuits, the power supply might very well be designed through either a current or thermal trip to shut down in case of an overload.

As this is a card you apparently have added yourself, you shouldn't expect the supplied PSU to be dimensioned to handle such a load. Keep in mind that the typical idle power consumption of a desktop computer is 60 W, and on the order of twice that might be a reasonable figure for a fairly typical computer (except the monitor) under load.

You should look for a power supply that is rated for the necessary load on the appropriate rails. Since you'd need to supply at least around 50 A on 12 V (600 W there alone) to guarantee enough power for the graphics card if it really draws 500 W, you'll be looking at power supplies at least in the 800 W and up range. If the graphics card draws on the order of 250 W, you might easily get away with a 500 W PSU. What is most important (more so than the total wattage rating) is to pay close attention to the rated amperages on the different rails and the requirements of your particular graphics card and through the motherboard the CPU (since those two by far will consume most of the power unless you have an insane number of other pieces of equipment in the computer) so you don't end up with another power supply that exhibits the same problem.

It is possible that the power supply is faulty and causing the PC to shut down.

Your hypothesis that a system would reboot if there is a CPU or Motherboard fault is reasonable, although it is conceivable that it could cause a shutdown (particularly the motherboard).

If you need to leave the PC for a few minutes before a reboot will work, this is also a strong indicator of a PSU problem.

It does seem to me that that size power supply (unless its a very good one - unlikely at $30) might be on the low side. The GPU has a TDP of 230 watts by itself, with the CPU having a TDP of 77 watts, so thats 305 watts excluding the motherboard and CPU - so your 480 watt figure sounds right. I'd be inclined to believe the PSU might have been working too hard and is now not able to handle the load.

To answer your first two questions: Yes, and no.

I'd lean more towards a PSU myself, as that power supply that they? provided you is absolutely garbage as their 12V ratings are very low. When the 12V is overloaded it can cause the whole PC to reboot, and with a 770 you're definitely pushing the limit on it. If you're comfortable enough working inside the computer and you've got a video connector on-board your motherboard, try unplugging the GPU's PCI-E cables that lead to the power supply, move the video input to the on-board video connected to the motherboard and boot up your computer for a while. If it stays stable longer than "several hours", you've probably narrowed down your issue. You'll need to contact whoever sold you that thing and have them get you a power supply that isn't made from the junkyard scrap.

Does the PSU capacity decrease over lifetime of the PSU?

• PSUs, like most modern appliances, broke with time. Cheap PSUs broke faster. But yours is a new one.

Does the PSU capacity temporarily decrease as it is active for a continious time?

• It depends on the load and the quality of the electronics.

PSU is one of the most important parts when you are building a rig, and yet it is often one of the most overlooked parts, along with the motherboard. PC vendors usually mount cheap PSUs to cut costs, even in medium to high end PCs. You need to decide whether you would want to keep going on for some time with a crappy PSU and replace it when it brokes, or buy a good one from the beginning that would work fine for your PC's lifespan. Being a high-end PC I would choose the latter, specially because a faulty PSU can fry your motherboard when it stops working normally.

I personally have bought a high end PC in the past, and I selected one of the best mobo's at the time, good GX card, best HDD, everything from reputable brands. But the vendor sold me a cheap $40 PSU. It wasn't the cheapest available though. Two years later it started failing randomly, causing boot loops. Turned out a capacitor has blown out. Replaced it with a decent PSU (Corsair) and everything is ok.

So my advice: go to the store where you bought the PC and have them diagnose the PSU. If it turns out to be faulty, try to replace it for a better one, and pay the difference. Spare no expense on it, expect to expend $100+ on a good one if it is brand new.