When you switch on or reset you PC it performs a diagnostic test called a Power-On Self Test (POST) to check that all the components are present and working correctly.
First, it checks core components such as the system clock, processor, RAM, keyboard controller and graphics card. If any device fails this part of the POST, you'll hear series of beeps sound from from the desktop computers.
After the graphics card has passed its test, the BIOS can then indicate any errors onscreen, such as the classic "Keyboard error or no Keyboard present. Press F1 to continue" message.
Below are the list of common beep codes for popular BIOSes. Check out!
→ ONE LONG, TWO SHORT BEEPS Graphics card error (reseat or replace graphics card)
→ ONE LONG, THREE SHORT BEEPS No graphics card, or graphics memory error (install or replace graphics card)
→ TWO SHORT BEEPS Memory error (reseat or replace memory)
→ ONE HIGH-PITCHED BEEP Processor overheating symptoms
→ ONE HIGH-PITCHED BEEP, ONE LOW PITCH BEEP Processor error music
→ ONE BEEP All ok
→ TWO BEEPS Memory parity error (reseat or replace memory)
→ THREE BEEPS Memory read or write error (reseat or replace memory)
→ FOUR BEEPS motherboard timer is not working properly
→ FIVE BEEPS Processor or memory error (reseat or replace processor and memory)
→ SIX BEEPS Keyboard controller failure (replace motherboard)
→ SEVEN BEEPS Processor exception interrupt error (reseat or replace processor)
→ EIGHT BEEPS Display memory read or write failure (reseat or replace graphic card)
→ NINE BEEPS BIOS ROM Checksum errors (replace BIOS chip motherboard)
→ TEN BEEPS Bad cache memory (replace cache memory if possible)
→ ONE LONG, THREE SHORT BEEPS Memory error (reseat or remove any memory recently added and reseat all other memory)
→ ONE LONG, EIGHT SHORT BEEPS Graphic card error (reseat ghraphics card)
Phoenix BIOSes produce a series of beeps separated by a pause. For example: beep... beep beep beep...beep... beep would be 1-3-1-1
→ 1-1-4-1 Level 2 cache error (reseat or replace the processor)
→ 1-2-2-3 BIOS ROM checksum (replace BIOS chip or motherboard)
→ 1-3-1-1 Memory refresh test failure (reseat or replace memory)
→ 1-3-1-3 Keyboard controller failure (replace the motherboard)
→ 1-3-4-1 Memory failure (reseat or feplace memory)
→ 1-3-4-3 Memory refresh test failure (reseat or replace memory)
→ 1-4-1-1 Memory refresh test failure (reseat or replace memory)
→ 2-1-2-3 BIOS error (refresh BIOS chip or motherboard)
→ 2-2-3-1 IRQ problem (remove expansion card or replace motherboard)