PSU Too Weak

[kareed44]

What are the symptoms of a PSU being under powered for the card it paired with?

I ask this because I have a situation where I know the PSU is too far too weak (300W for GTX480) for the graphics card. I tried to see what would happened if I just tried it anyways to get the drivers installed, while I wait for my PSU upgrade to ship.

The system wouldn't even recognize the card when I tried to install the drivers, but the fan on the card was actually running. Does this sounds about right? If the PSU isn't putting out enough power, should the NVidia driver installer still recognize the card as existing?

 

[vmem]

What are the symptoms of a PSU being under powered for the card it paired with?

I ask this because I have a situation where I know the PSU is too far too weak (300W for GTX480) for the graphics card. I tried to see what would happened if I just tried it anyways to get the drivers installed, while I wait for my PSU upgrade to ship.

The system wouldn't even recognize the card when I tried to install the drivers, but the fan on the card was actually running. Does this sounds about right? If the PSU isn't putting out enough power, should the NVidia driver installer still recognize the card as existing?

your card would try to draw enough power to run, but your PSU will not support that much. if you have a good PSU, your computer will be stuck in a reboot loop at bios while it tries to start. and after enough tries it'll just shut down. if you have a bad PSU without safeties, your card can draw too much load and overload the PSU, shooting a surge to the rest of your components and your computer can go down in flames (sometimes literally ). I'm not trying to scare you, don't try this

 

[Deemo13]

Basically, one of two things will happen.

On a good 300W, it should not let you run the computer when the power required is exceeding what the power supply itself can put out. It should automatically shut off and come up with errors and what not. Good power supplies have precautions and such.

On a generic 300W on a regular computer, most likely like the one you have:

http://www.youtube.com/watch?v=wOjJOXIJNt4

The power supply will attempt to put out more wattage required, and will most likely blow itself up in the case of a 480, which I'm pretty sure uses more than 300W by itself. The power supply will blow a few capacitors and might actually take some of the components with it on its way out.

 

[kareed44]

Neither of these things happened.

The computer booted just fine. I heard Windows boot up (log in sounds and everything), but the screen was black. I swapped the display connector over to the on board graphics, and the screen came up and everything appeared normal (like before the 480 was in there). Only difference was I had a 480 in my system with the fan running doing nothing.

I wont try to do this again given that it could destroy my PC, I just want to know that when the new PSU arrives, it will work.

The NVidia driver installer didn't even know the card was there and it was the correct drivers. This was the case with both the supplied drivers on the EVGA disc and the drivers I downloaded. (the drivers on the disk were reference anyways)

 

[vmem]

um, the drivers don't recognize your card because as far as your machine's concerned, the card isn't there. sure the fans may spin, but the card needs like 250W to boot up and be recongnized

 

[djscribbles]

What you saw is perfectly reasonable, but as others have said, your outcome was lucky.

In general, this article pretty much sums up the failure modes for a power supply that is pushed past it's limits:
http://www.tomshardware.com/reviews/low-cost-psu-pc-power-supply,2862.html