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Thread: Locking the BIOS?




  1. #21
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    Default Re: Locking the BIOS?

    The reason why I wasn't too worried about standoffs was that a few years ago I got a mb which came complete with plastic standoffs so never really associated them with electricity supply.

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  2. #22
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    Default Re: Locking the BIOS?

    While I agree you MUST use standoffs, your cardboard insulator was not a bad idea, even if it did not work perfectly. OTOH, I look at the hundreds of bare contacts floating a few millimeters above the mother board tray when standoffs are used, and I think, is this really a good system? It works, but just barely.

    I would not feel bad if I were you, it could be worse. A recent post mentioned how someone was removing their mobo to RMA it, when the PC started... because the PS was on, still connected to the board, and connected to AC power!

  3. #23
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    Default Re: Locking the BIOS?

    Quote Originally Posted by parsec View Post
    While I agree you MUST use standoffs, your cardboard insulator was not a bad idea, even if it did not work perfectly. OTOH, I look at the hundreds of bare contacts floating a few millimeters above the mother board tray when standoffs are used, and I think, is this really a good system? It works, but just barely.

    I would not feel bad if I were you, it could be worse. A recent post mentioned how someone was removing their mobo to RMA it, when the PC started... because the PS was on, still connected to the board, and connected to AC power!
    But does the MB actually use the metal chassis of the case as an earth?

    Because it seems a particularly bad idea to me if I think about it (which I never have before), and looking at another mb it doesn't actually look as if it does, since there doesn't seem to be a backplane in that area (or any area really) - all of the back of the mb is varnished except where the flow soldering has taken place and the scews on the front side also seem to have no electrical connection to anything with the standoffs merely acting to provide placement and rigidity to the mb and stop it from shorting out via the soldered connections.

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    Last edited by petersmart; 11-28-2012 at 01:38 AM.

  4. #24
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    Default Re: Locking the BIOS?

    The earthing of the chassis is not necessarily related here, as much as short circuits on the mother board, when the component pins on the bottom of the board touch the mother board tray/case under it. Yes that part may be painted, but the pins/wires on the bottom of the board may scratch through the paint, and zap, a short.

    Regarding earthing/grounding of the case, let's start with the PS. The PS case is connected to the third wire earth/ground wire of the AC power cord. The PS case is screwed to the PC chassis with four screws. Yes, the PS case and PC case are painted, but at least one of the screws will wear off the paint, or touch bare metal on the screw threads.

    Also, the screw holes on the mobo have contacts around the holes that are conductive. Metal standoffs screwed into the case are making electrical contact with it, and the mobo screws touch the standoffs and mobo contacts.

    Then there are all the earth/ground wires from the PS cables to the mobo. That does not cover everything, but it's clear that the number of earth/ground connections between the mobo, PS, and PC case are many.

  5. #25
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    Default Re: Locking the BIOS?

    Electrically speaking earth ground is actually a voltage reference point. having a power supply earthed with the motherboard not earthed *CAN* produce extreme voltages... but it's pretty rare. however having the MB grounded as well as the power supply to the same reference point (earth) eliminates that problem entirely

    This is one of the reasons why I dislike when people put their motherboard on a table... they are relying on the power supply manufacturer to provide a proper ground reference to the motherboard.

    Floating ground is a bad thing, read this

  6. #26
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    Default Re: Locking the BIOS?

    Quote Originally Posted by synack View Post
    Electrically speaking earth ground is actually a voltage reference point. having a power supply earthed with the motherboard not earthed *CAN* produce extreme voltages... but it's pretty rare. however having the MB grounded as well as the power supply to the same reference point (earth) eliminates that problem entirely

    This is one of the reasons why I dislike when people put their motherboard on a table... they are relying on the power supply manufacturer to provide a proper ground reference to the motherboard.

    Floating ground is a bad thing, read this
    But surely the mb is earthed - through the main power supply plug to the board - the 24 pin plug and the 4 pin plug?

    And as I say a few years ago I got a mb with plastic standoffs supplied by the mb manufacture themselves.

    And after Googling this it seems most opinion is that the standoffs are only there to stop shorts from the underside of the board.

    And the reference you supply seems to deal mostly with electrical appliances where an unintentional floating ground can be lethal.

    .
    Last edited by petersmart; 11-28-2012 at 04:00 AM.

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