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Recently I had some problems with USB devices (never had that before). My mouse, my keyboard and my wireless adapter sometimes just wouldn’t work anymore for some reason. Yesterday I got a message from Windows, that my USB ports wouldn’t deliver enough power for my devices to run.

Today my PC just didn’t start anymore until I unplugged most of my devices. Now with only mouse, keyboard and wireless it works fine. As soon as I plug in more devices the PC won’t start.

My System: Windows 8 64 Bit, Asus P9X79 Pro, I7 3930k, GTX 480, 16 GB DDR3 Ram

I have a pretty old power supply (about 6 years old). It’s 700 watts and I never had problems, so I never changed it. Could it be the power supply or is it something with the mainboard?

What I already did:

  • I reinstalled the mainboard’s drivers
  • I changed USB settings in the BIOS so it wouldn’t save energy
  • I updated to the latest version of the BIOS

Anyone any idea what it could be or how to test the power supply (I have no tools).

Thank you very much.

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1 Answer 1

I highly doubt it is USB that is drawing out all your power. Most motherboards cannot output more than 2.5 watts of power over USB. It is most likely to be your power supply.

It is very difficult to test the power supply without tools other than attaching one part at a time and seeing at what point it gives out. Some backup power supplies will display how much wattage is being pulled.

Honestly, I would just get a new power supply.

Edit: You could also try the power supply with another computer with a power draw that is in range of what the power supply is rated at. This could eliminate the question of whether it is a problem with the power supply or motherboard.

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If I unplug most of my usb devices the PC works, otherwise it doesn't. So it must be a usb related problem. Could a broken usb device be responsible for the PC not starting? –  Ben Jul 29 '13 at 18:00
    
Only thing I could think of is a USB driver causing windows to fail on boot. –  Franz Payer Jul 29 '13 at 19:08
    
It's not windows that fails to boot, the whole computer (not even the fan) won't work if all devices are plugged in. –  Ben Jul 30 '13 at 12:40
    
Do you have a video card with a lower power draw to see if that fixes it? –  Franz Payer Jul 30 '13 at 13:38
    
No I don't but I removed the soundcard and it had no effect –  Ben Jul 30 '13 at 21:25

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