Power On Self Test

What is a Power On Self Test (P.O.S.T.)? This site is dedicated to answering that and other BIOS (Basic Input Output System) related questions. Every computer has a BIOS. Every BIOS outputs the POST. Understanding what happens to your computer during this stage is key to obtaining better peformance and for troubleshooting all problems with your PC.

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What is the Power On Self Test?

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The POST (power on self test)

The Power On Self Test is a function of the motherboards BIOS. We will discuss the actual BIOS in other sections so for now I will provide only minor details. If you feel you need to know more about the BIOS before continuing click this link: BIOS

The Power On Self test Occurs to provide you the end user information about your computer. It is used mostly as a diagnostic tool.

The Power On Self test will provide you with two forms of BIOS related diagnostic information:

1) Beep Codes

2) POST codes

Continued here: Power On Self Test

What are POST Codes?

POST codes as mentioned in section 1 are different for all three BIOS manufacturers. POST codes provide a visual two character readout that shows at what stage the Power On Self test is at.

How do I see my motherboards POST codes? You need a POST card. Some of the newer motherboards provide built in POST diagnostic capability. Most still do not.

You can see an example of a POST card on the next page.and even purchase one at a great price.. They can be used on any motherboard with a 32bit PCI slot.

Click to read more about the POST and some diagnostic POST tools like POST Cards also known as port 48 or PCI test cards here: POST Codes.

What are Beep Codes?

Each BIOS company, Award, AMI and Phoenix have different beep codes. Beep codes occur if your motherboard has a built in speaker. Most chassis have a speaker connector also so if your motherboard didnt come with a built in speaker it usually comes with a 4 pin speaker header.

Beep codes occur if the board is functioning normal or if there are problems. In most cases you here one beep if the board is POSTing ok.

There are quite a few beep codes so a chart is necessary to analyse them. You can view these charts from this page: beep codes, but keep reading for now if you want to learn more.

Beeping is actually a good sign even if your computer isn't booting. The reason why its still a good sign is that if its beeping there is CPU functionality and the POST is performing to some level.

Read more about beep codes here: beep codes

All the links above take you to more information about the POST and BIOS, here are some more external links:

Read more info on POST at my main site:

http://www.biosman.com

or go to the Wikipedia site page:

http://en.wikipedia.org/wiki/Power-on_self-test

To read more about the basic input output systen (BIOS) or the basic input/output systems however you want to call it, go to my other site:

http://www.basicinputoutputsystem.com