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Thread: USB and 12v Rail

  1. #1
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    USB and 12v Rail

    Hello,

    I know very little about electricity. I have a question. If my motherboard/CPU is taking power from the 12V rail on my PSU. Would it stand to reason that any usb devices (wifi, Bluetooth) would also draw their power from that same 12V rail? I am trying to figure out how much power i am going to need, and already have alot of external usb devices that do not require external power adapters.

    Thanks!

  2. #2
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    Quote Originally Posted by Balkos View Post
    Hello,

    I know very little about electricity. I have a question. If my motherboard/CPU is taking power from the 12V rail on my PSU. Would it stand to reason that any usb devices (wifi, Bluetooth) would also draw their power from that same 12V rail?
    Nope, they take it from the 5v rail. Converting Voltage takes room on the board, and generates heat. Instead, the voltage is created in the PS.

    Quote Originally Posted by Balkos View Post
    I am trying to figure out how much power i am going to need, and already have alot of external usb devices that do not require external power adapters.

    Thanks!
    I believe the USB spec is 250ma per device, though it MIGHT be 500ma.

    Michael
    ...I love the French language...especially to curse with...Nom de Dieu de putain de bordel de merde de saloperies de connards d'enculés de ta mère. You see, it's like wiping your *** with silk, I love it.

  3. #3
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    Every device gets 100mA at startup and can request up to 500mA for general operation.

  4. #4
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    alright forget this question. I was not thinking right when i asked it.

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