Power On Self Test (Post)

In this article, We will know what is the Power On Self Test, describes the error codes and beeps sound that can help for solving the issue.

Power on Self Test

What is POST(Power On Self Test)?

The power-on self-test is a diagnostic program used to check all the hardware components are working properly or not. Post checks the processor, memory, peripheral devices, video, and all components and reports for error if any in the form of error codes or beeps. If the POST is successful the computer starts bootings. Booting is the process of loading the Operating system into system memory.

What is the Function of BIOS during POST (Power on Self Test)?

The main function of BIOS during POST are given below-

  • Check for the integrity of the BIOS code.
  • Check for the size of the system memory and verify its integrity.
  • Discover, initialize the list of all system buses and devices.
  • Identify organize and select the devices for booting. The priority of the bootable devices can be clearly identified.
  • Helps to start the Operating System.
  • Display error codes or beep sounds if there is any problem with the device.

List of Error beeps of POST (Power On Self Test)

The some of the Error beeps of POST are followings-

  • Short beep– Normal POST- System is OK.
  • 2 short beeps– POST Error code is shown on screen.
  • No beep- Power supply or system board problem.
  • Continuous beep- Power supply, system board, or keyboard problem.
  • Repeating short beeps– Power supply or system board Problems.
  • 1 long, 1 short beep- System board Problem.
  • 1 long or 2 short beeps- Display adapter problem.
  • 1 long, 3 short beeps- Enhanced Graphics Adapter.
  • Long Beeps– 3270 keyboard card.

The list of Stand Error codes from Numbers is below

  • 100 to 199- System board Issue.
  • 200-299 – Memory Problem.
  • 300-399- Keyboard Problem.
  • 400-499- Monochrome display problem.
  • 500-599- Colour/ graphics Display problem.
  • 600-699- Floppy Disk drive or adapter problem.
  • 700-799- math coprocessor issue.
  • 900-999- Parallel Printer port issue.
  • 1000-1099- Parallel printer port Issue.
  • 1100-1299- Asynchronous communication device, adapter, or Port.
  • 1300-1399- Game Port issue.
  • 1400-1499- Colour/ Graphics Printer issue.
  • 1500-1599- Synchronous communication Device, adapter, or port issue.
  • 1700-1799- Hard Drive or Adapter Issue.
  • 1800-1899- Expansion Unit Failure.
  • 200-2199- Bisynchronous communication adapter issue.
  • 2400-2599- EGA system board Video Issue.
  • 3000-399- LAN adapter issue.
  • 4800-4999- Internal Modem Issue.
  • 7000-7099- Phoenix BIOS chips.
  • 7300-7399- 3.5-inch disk drive issue.
  • 8900-8999- MIDI Adapter Issue.
  • 11200-11299- SCSI adapter Issue.
  • 21000-21099 -SCSI fixed disk and Controller issue.
  • 21500-21599- SCSI CD-ROM issue.

2020:Computer Hardware Terms and Descriptions

2 thoughts on “Power On Self Test (Post)”

Leave a Comment