Definition of Power-On Self Test (POST) in the Network Encyclopedia.
What is Power-On Self Test (POST)?
Power-On Self Test is a special set of ROM routines that run whenever a PC is booted. The power-on self test (POST) is designed to test whether system components are functioning properly before attempting to boot the operating system, and checks such things as the RAM, keyboard, and disk drives.
If a problem is detected during the POST, the system typically emits a series of beeps and displays a corresponding error message giving some indication of the problem.
Specific problems are indicated by different numbers of beeps, but the interpretation of these varies depending on the BIOS used.
AMI WinBIOS
On newer Pentium II or III systems that use the popular AMI WinBIOS, use the following table to interpret the number of beeps in order to troubleshoot the problem.
POST Beep Codes for AMI WinBIOS
| Number of Beeps | Problem | Resolution |
| 1, 2, or 3 | Memory error | Check speed and voltage of dual inline memory modules (DIMMs), try reseating DIMMs, or replace DIMMs |
| 4 | Timer error | Replace motherboard |
| 5 | CPU error | Try replacing CPU, or replace motherboard |
| 6 | Gate A20 error | Try reseating keyboard controller chip, try replacing keyboard controller chip, or replace motherboard |
| 7 | Interrupt error | Replace motherboard |
| 8 | Video memory error | Try reseating the video RAM (VRAM), try replacing the VRAM, or replace video card |
| 9 | BIOS ROM error | Replace BIOS ROM chip |
