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I am wondering what will be the symptoms if high end gaming video card does not get enough power because the PSU is not powerful enough. Some high end video cards list their requirements as lets say 550W but they work with PSU of 400W.

So what happens in this case? Will the PC shut down undr load or maybe the hardware will not perform to its maximum (for example will not produce as many FPS)?

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If the system gets into a state where the power supply is not sufficient the system will most likely crash. –  Robert Aug 30 '12 at 18:03
    
I overloaded my PC's power supply once upon a time. The PC wouldn't power on the first time I tried it, it would power on every other time - not even kidding. It was weird and generally not a good position to be in. Basically the problem was that the system started out marginally ok for power and then I tried to hang a ton of USB devices off of it. –  Mark Allen Aug 30 '12 at 18:18

2 Answers 2

up vote 4 down vote accepted

You risk overdrawing the PSU and damaging it. It can also cause other components to not get enough power or deal with erratic power from an overloaded PSU, so unrelated things may also start to act up. Better quality PSU's are probably going to be more robust than lower quality cheap OEM provided ones.

A video card or other component may be say it needs a 550w power supply, and it probably does only when fully loaded. So you may not experience problems on power on, but only after playing a game or something else that stresses the GPU.

Specific symptoms include:

  • lockups
  • BSODs
  • graphical corruption
  • display goes black

You can try "burning-in" your card by running a benchmark utility such as FurMark3d or similar for an extended time, giving problems a chance to surface. But don't do it if you know your PSU is underrated. Get a new PSU.

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Buying tip: Your system's power draw should be about 80% of the rated amount on your PSU under load. –  Darth Android Aug 30 '12 at 19:32

In cases I have seen, the PC wont even power on, as the power supply detects that to much power is being drawn. In other cases, where the PC boots, but under load the graphics card begins to behave poorly. Examples include, BSODs, shutdowns, and incorrect graphical display.

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