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The Power-On Self-Test (POST) is a self-diagnostic program that runs a test on RAM, I/O devices, and the CPU on system startup. The POST is stored in the ROM BIOS and requires at least a processor, memory, and video adapter to complete its diagnostic tests. The POST recognizes errors related to BIOS configuration settings and I/O connectivity, such as a stuck keyboard. Be forewarned: you may be asked to identify errors the POST might not recognize. Table 2.3 lists some examples of POST numeric error codes that you may encounter while using a computer. There is a good chance you may also encounter one or two POST numeric error code questions on the test.
Error Code | Error Associated with Code |
---|---|
1XX | System board error |
201 | Memory error |
301 | Keyboard error |
5XX | Monitor error |
601 | Floppy drive/adapter error |
1101 | Serial card error |
1701 | Hard drive controller error |
There are also sounds or beep codes associated with POST operations and system startup to alert you in the event of an error. BIOS manufacturers, such as IBM, Phoenix, and Award, each provide their own distinct set of beep codes. A list of IBM's common beep codes is provided in Table 2.4. It is likely that the test will focus on numeric error codes. If you are interested in learning more about beep codes specific to BIOS manufacturers that are not listed, you should consult that manufacturer's Web site.
Beep Description | Error Associated with Beep |
---|---|
No beep | Motherboard or power failure |
One short beep | All POST operations completed successfully |
Two short beeps | POST error |
One long beep, one short beep | Motherboard error |
One long beep, two short beeps | Video adapter failed |
One long beep, three short beeps | Video adapter error |
Three long beeps | Keyboard failure |
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