The computer POST (Power On Self Test) tests a computer, to make sure that it meets the necessary system requirements before booting up.
If your PC does not even turn on (no lights, no sound, no fans running, etc.) this is not a POST problem so no beeps will be heard. This situation is likely to be a power related issue.
If your PC does power up but then fails the POST (Power On Self Test) , the computer normally returns a beep code indicating the problem that's preventing the computer from starting.
Generally, if the computer completes the POST, you will receive a single beep and the Operating system will start to load (with some BIOS manufacturers the computer may beep twice and then boot up).
| Beep Code | Meaning |
|---|---|
| one long | Passed (no errors) |
| one short | DRAM memory refresh failure |
| 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, two short | Video failure |
| one long, three short | Base/Extended Memory failure |
| one long, eight short | Display/Retrace Test failure |
| Beep Code | Meaning |
|---|---|
| one short | Passed (no errors) |
| two short | Any non-fatal error |
| one long, two short | Video failure |
| one long, three short | Keyboard Controller failure (applies to 286, 386 and 486) |
| Beep Code | Meaning |
|---|---|
| one short | Passed (no errors) |
| two short | General BIOS error - remedy unknown |
| one short, two long | Memory Module |
| one long, one short | BIOS ROM checksum error |
| one long, two short | Video error |
| 7 Beeps: one long, one short, one long, one short, pause, one long, two short |
AGP Video |
| one long continuous tone | Also Memory Module |
| Beep Code | Meaning |
|---|---|
| none | Power Supply or System Board failure (possible short) |
| one short | Passed (no errors) |
| one short (blank screen) | Video error (check cable) |
| one short (no boot) | Floppy Drive error |
| two short | Configuration Error (displayed on screen) |
| repeating short | Power Supply or System Board failure |
| continuous | Power Supply or System Board/Keyboard stuck |
| one long, one short | System Board failure |
| one long, two short | Video (Mono/CGA) failure (check cable) |
| one long, three short | Video (EGA) failure (check cable) |
| three long | Keyboard Card error |
| Beep Code | Meaning |
|---|---|
| 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 (followed by various combinations) | First 64K RAM Chip/Data Line failure (combinations indicate which 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 | Real time 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 |
| Beep Code | Meaning |
|---|---|
| one short | Low level processor verification test failed |
| two short | Clearing keyboard controller buffers failed |
| three short | Keyboard controller reset failed |
| four short | Low level keyboard controller interface test |
| five short | Reading data from keyboard controller failed |
| six short | System board support chip initialisation failed |
| seven short | Processor register read/write verify test failed |
| eight short | CMOS timer initialisation failed |
| nine short | ROM BIOS checksum test failed |
| ten short | Initialise primary video |
| eleven short | 8254 timer channel 0 test failed |
| twelve short | 8254 timer channel 1 test failed |
| thirteen short | 8254 timer channel 2 test failed |
| fourteen short | CMOS power-on and time test failed |
| fifteen Short | CMOS shutdown byte test failed |
| one long | DMA channel 0 test failed |
| one long, one short | DMA channel 1 test failed |
| one long, two short | DMA page register test failed (POST 18) |
| one long, three short | Keyboard controller interface test failed |
| one long, four short | Memory refresh toggle test failed |
| one long, five short | First 64 KB memory test failed |
| one long, six short | Setup interrupt vector table failed |
| one long, seven short |
Video initialisation failed |
| one long, eight short |
Video memory test failed |
| Beep Code | Meaning |
|---|---|
| one | Passed (no errors) |
| two | Video adapter error |
| three | Keyboard controller error |
| four | Keyboard error |
| five | PIC 0 error |
| six | PIC 1 error |
| seven | DMA page register error |
| eight | RAM refresh error |
| nine | RAM data error |
| ten | RAM parity error |
| eleven | DMA controller 0 error |
| twelve | CMOS RAM error |
| thirteen | DMA controller 1 error |
| fourteen | CMOS RAM battery error |
| fifteen | CMOS RAM checksum error |
| sixteen | BIOS ROM checksum error |
| Beep Code | Meaning |
|---|---|
| one long | Passed (no errors) |
| two long | Video adapter error |
| one long, one short, one long |
Keyboard controller error |
| one long, two short, one long |
Keyboard error |
| one long, three short, one long |
PIC 0 error |
| one long four short, one long |
PIC 1 error |
| one long, five short, one long |
DMA page register error |
| one long, six short, one long |
RAM refresh error |
| one long, seven short, one long |
RAM data error |
| one long, eight short, one long |
RAM parity error |
| one long, nine short, one long |
DMA controller 0 error |
| one long, ten short, one long |
CMOS RAM error |
| one long, eleven short, one long |
DMA controller 1 error |
| one long, twelve short, one long |
CMOS RAM battery error |
| one long, thirteen short, one long |
CMOS RAM checksum error |
| one long fourteen short, one long |
BIOS ROM checksum error |
| Beep Code | Meaning |
|---|---|
| one short | Passed (no errors) |
| two short | CMOS IC error |
| one long, two short | Video error |
| one long, three short | Peripheral controller error |
| Tones | Meaning |
|---|---|
| Error Tone. (two sets of different tones) | Problem with logic board or SCSI bus |
| Startup tone, drive spins, no video | Problem with video controller |
| Powers on, no tone | Logic board problem |
| High Tone, four higher tones | Problem with SIMM |
Read more articles about PC repairs, Web design & SEO