Computer POST
At startup computers run through a pre-boot check list of items to ensure everything is hunky dory with the attached hardware components. The process is known as POSTing. POST is an acronym for Power On Self Test.
A fully functional computer will normally give a single beep at bootup. The single beep indicates everything is okay and will continue with the boot process and load the operating system.
If the computer gives any other beeps or no beeps, you have a problem.
Common BIOS systems beep codes:
AMI (American Megatrends') BIOS | |
Beep Codes | Message |
| one short | DRAM refresh failure (Problem with memory) |
| two short | Parity circuit failure |
| three short | Base 64K RAM failure |
| four short | System Timer failure |
| five short | Processor failure |
| six short | Keyboard Controller / Gate A20 failure |
| seven short | Virtual Mode Exception error |
| eight short | Display Memory Read/Write failure (fault with video card) |
| nine short | ROM BIOS Checksum error (fault with BIOS chip) |
| ten short | CMOS Shutdown Read/Write error |
| eleven short | Cache memory |
| one long | Passed (no errors) |
| one long, two short | Video failure |
| one long, three short | Base / Extended Memory failure |
| one long, eight short | Display / Retrace Test failure |
Phoenix BIOS | |
Beep Codes | Message |
| one, one, three | CMOS Read/Write |
| one, one, four | ROM BIOS Checksum failure |
| one, two, one | Programmable Interval Timer failure |
| one, two, two | DMA Initialisation failure |
| one, two, three | DMA Page Register Read/Write failure |
| one, three, one | RAM Refresh Verification error |
| one, three, three | First 64K RAM Chip/Data Line failure |
| one, three, four | First 64K RAM Odd/Even Logic |
| one, four, one | First 64K RAM: Address Line |
| one, four, two | First 64K RAM: Parity failure |
| one, four, three | Fail-Safe Timer Feature (EISA only) |
| one, four, four | Software NMI Port failure (EISA only) |
| two (plus combo) | First 64K RAM Chipfailure (combo indicates bit) |
| three, one, one | Slave DMA Register failure |
| three, one, two | Master DMA Register failure |
| three, one, three | Master Interrupt Mask Register failure |
| three, one, four | Slave Interrupt Mask Register failure |
| three, two, four | Keyboard Controller failure |
| three, three, four | Display Memory failure |
| three, four, one | Display Retrace failure |
| three, four, two | Video ROM search proceeding |
| four, two, one | Timer Tick failure |
| four, two, two | Shutdown failure |
| four, two, three | Gate A20 failure |
| four, two, four | Unexpected Interrupt in Protected Mode |
| four, three, one | RAM test above 64K failure |
| four, three, two/three | Programmable Interval Timer, Channel 2 failure |
| four, three, four | Realtime Clock failure |
| four, four, one | Serial Port error |
| four, four, two | Parallel Port error |
| four, four, three | Math Co-processor failure |
| (tone) one, one, two | System Board Select |
| (tone) one, one, three | Extender CMOS RAM |
Check the series of beeps (or lack of) against the tables and its a starting point for troubleshooting your system.
That's about it.
