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POST

Power-On Self Test

An explanation of the proper boot sequence of a device or computer, why it is important, and what could happen if it did not exist.

Episode #4-28 released on March 29, 2014

Power-On Self Test, known as POST, is the process of hardware and software testing itself when the device loads to ensure everything works, after which the bootstrap protocols take over turning on the device. For computers, a computer POST usually finished with a single beep telling us it is okay, while loading the BIOS or UEFI, then the operating system in question.

What is POST important?

It ensures that all the equipment actually works, when a computer or device cannot POST, it means something is wrong.

How do we know what is wrong when a device or computer cannot POST?

We can kind of tell by the number and duration of beeps the computer or device emits when POST fails. There are plenty of web-sites who post this information, such as the one in my sources for this episode.

Are there issues that can prevent any notification resulting for POST failure?

POST notification requires that the main board functions, at least in part, correctly. If a main board cannot power itself correctly as to start the Power-On Self Test, then the main board is probably the issue. Sometimes defective RAM can be to blame, and removing the defective RAM is enough to allow for normal POST functionality, and the computer may even start normally, if the RAM is the originating issue.

Computer does not POST, what do I do next?

This is a common enough issue, that a procedure actually exists, however some of the tips given can affect computers with RAID configurations.

First, unplug everything from the main board, except what is required to use the computer, basically you only require a graphics card or the on-board video, and keyboard. All hard drives, optical drives, and accessory cards should be removed from the computer. At this point attempt to power the computer. If you have more than one bar of RAM, consider removing all but one, and trying to boot with them one at a time.

Second, if your computer can start, only plug in one accessory at a time, and once identified as functional, unplug and put aside as known to work. If you come across something that does not allow the computer to load, put it aside as known failed.

Third, once you have identified all the known working components, put them all into the computer, and try POSTing once more. If the computer starts, you have found the items blocking your computer from POSTing. If POST failure reoccurs, try plugging in one piece a time until the computer stops working, remove the piece in question, and try another piece. You may find that POST can fail due to hardware mismatching.

For any piece still under warranty, you may either send back to the manufacture, or bring it back to the store if you have an extended warranty plan on it.

If at any point you can not get your computer to POST, at all. Your most likely culprits are either your main board, processor, BIOS failure, power supply, or some other chip on the main board.

Last question, why is POST important?

If a computer or device tried to load without knowing it was safe to power, the device can actually fail catastrophically damaging sensitive components such as the hard drives that can the data, as oppose to a soft failure such as not booting.

Host : Steve Smith | Music : Jonny Lee Hart | Editor : Steve Smith | Producer : Zed Axis Productions

Sources & Resources