How to Build Your Own Pentium III Computer
Install the Motherboard
Last updated: 4/14/99

  There are six mounting holes on the motherboard:  three at the front and three at the back.   There more than six holes where you can screw-in the brass standoffs (the HX45 Assembly Instructions calls them studs) used  to secure the motherboard to the case and more than six standoffs come with the case.  Set the motherboard with the anti-static bag on top of the side of the case.  Use it as visual guide to screw six standoffs to the case.  Screw-in the standoffs by hand and then use a socket driver to tighten them (you could use an adjustable wrench or pliers if you are careful).

Do not over-tighten.  What remains can be very difficult to remove when they break.  Count them to verify there are six.

  Gently place the motherboard in the case so the mounting holes are centered over their respective stand-offs.

Don't force the motherboard into the case--wiggle it into place if you have to.  If you see a mounting hole without a stand-off, you didn't install six of them or, worse, one of them is in the wrong hole and under the motherboard where it will short-it-out.  I've done it more than once.   It is a very common mistake.

  Inspect the back of the computer to see if the I/O connectors are aligned with their respective cutouts and that all of the appropriate blanks have been completely removed.  If necessary, loosen the screw on the I/O panel and adjust it .

  Attach the motherboard to the standoffs with six 6# -32*6L screws.

Other cases use a smaller screw.  I usually check alignment and screw-in one screw at the center of the rear of the board, check alignment again, and screw-in another at the front, followed by the remainder.  Do not over-tighten these screws or you could damage the motherboard.

  Double-check that you have secured the motherboard with six screws and that all of them properly seated (not cross-threaded). 

Besides securing the motherboard to the case, most or all--I can't see all four layers of the board--of these screws electrically ground the board to the case.

  Remove the rubber band from the front panel cables.

Attach the front panel cable labeled "POWER SW" to connector labeled "POWER-ON" on the motherboard (front of the motherboard, second row back, second pair of pins from the left).

Front panel connectors for this motherboard are installed with the label on the connector facing towards the back of the case.

  Connect the front panel connector labeled "SPEAKER" to the motherboard connector labeled "SPEAKER."

It is important to connect the speaker now so you can hear any BIOS error beeps when you first power-up the computer.  I do not install the rest of the front panel connectors until I'm sure I do not have to remove the motherboard.

  Remove the rubber band from the power supply connectors, untangle them and connect the ATX motherboard power plug  to the socket on the motherboard behind the CPU with clip facing towards the back of the case.  Push it down until it snaps into place.  It will only connect one-way.

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