P'O'S'T: Power On Self Test

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P.O.S.T Power On Self Test

• George Laur
• 1/25/08

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What is POST

• POST Stands for Power On Self Test
• POST occurs before the computer access the CMOS
• At this time, the computer is making sure that
  everything works.
• If the computer beeps once, then everythings
  fine.

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What is POST ? cont.

• If the computer beeps more than once, then you
  need to look up the POST Beep Codes for your BIOS
  to see what is wrong.
• Also, if you have video output, then some POST
  BIOS hexadecimal codes might show up.

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When POST Starts

• POST starts when the CPUs power good pin says
  that its ready to move on
• Once POST begins, it checks for the main
  components of your computer.
• When you hear 1 beep from your computer, then
  your computer moves on and everythings go.

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Errors

• If your computer beeps more than once at you, you
  have a problem.
• Record/remember the number of beeps, how long
  they are, and the sequence between the long and
  the short beeps. Shut your computer down after
  this.
• If you dont know what your BIOS is, then open up
  the case and see what you have.

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Errors cont.

• Once you know what BIOS you have, you can do one
  of a number of things
• Google BIOS Beeps, and look for a good site
• Google the company that made the BIOS, and look
  for the beep codes there (Not as easy as it
  sounds)
• OR, look in your motherboard book or other
  troubleshooting/maintenance book

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Common Errors

• Some common errors include
• Lack of keyboard/mouse connection
• No connection to hard drive
• Bad power supply, which is usually conveyed by a
  continuous string of beeps
• And CMOS error. This is sometimes due to a
  bad/dead CMOS battery

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What if I have an older computer?

• Within the past few years, computer companies
  have made it possible to upgrade a BIOS.
• This process is called flashing.
• This way, people dont have to buy new
  motherboards every two years.

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For those that drastically need help

• For those of you that are still lost, but want to
  be able to deal with POST problems and many
  others on their own, I would suggest buying a
  comprehensive troubleshooting, maintaining, and
  repairs guide. The one that I use is about ten
  years old, but it still works for problems that I
  have. It might not be on the market, but a
  similar guide would be useful for most people.