What Happens When a Computer Starts
- Power On -- The main system board keeps the CPU from running until the power supply is completely up.
- BIOS Startup -- The CPU reads and executes the BIOS program.
- POST -- Hardware is check for problems and if found beep codes will be heard.
- Video and Peripherals -- Any BIOS chips on the video or other cards are executed.
- System Diagnostics -- Memory, drives and other devices are checked and any errors will be displayed on screen.
- Plug and Play -- BIOS looks for PnP devices and sets IRQs
- Summary Screen -- Details of configuration are quickly displayed on screen.
- Boot -- BIOS looks for boot drive and runs code from the Master Boot Record(MBR)
- OS loads -- Operating system takes control.
Here is a listing of common beep codes. The codes may vary by mother board so check the manufacturers web site for the best listing.
Award BIOS Beep Codes
|
Beeps
|
Error
|
Description
|
| 1long, 2 short |
Video adapter error |
Either video adapter
is bad or is not seated properly. Also, check to ensure the
monitor cable is connected properly. |
| Repeating (endless loop) |
Memory error |
Check for improperly
seated or missing memory. |
| 1long, 3short |
No video card or bad
video RAM |
Reseat or replace the
video card. |
| High frequency beeps
while running |
Overheated CPU |
Check the CPU fan for
proper operation. Check the case for proper air flow. |
| Repeating High/Low |
CPU |
Either the CPU is not
seated properly or the CPU is damaged. May also be due to excess
heat. Check the CPU fan or BIOS settings for proper fan speed. |
AMI BIOS Beep Codes
|
Beeps
|
Error
|
Description
|
| 1 short |
DRAM refresh failure |
The programmable interrupt
timer or programmable interrupt controller has probably failed |
| 2 short |
Memory parity error |
A memory parity error has
occurred in the first 64K of RAM. The RAM IC is probably bad |
| 3 short |
Base 64K memory failure |
A memory failure has occurred
in the first 64K of RAM. The RAM IC is probably bad |
| 4 short |
System timer failure |
The system clock/timer
IC has failed or there is a memory error in the first bank of memory |
| 5 short |
Processor error |
The system CPU has failed |
| 6 short |
Gate A20 failure |
The keyboard controller
IC has failed, which is not allowing Gate A20 to switch the processor
to protected mode. Replace the keyboard controller |
| 7 short |
Virtual mode processor
exception error |
The CPU has generated an
exception error because of a fault in the CPU or motherboard circuitry |
| 8 short |
Display memory read/write
error |
The system video adapter
is missing or defective |
| 9 short |
ROM checksum error |
The contents of the system
BIOS ROM does not match the expected checksum value. The BIOS
ROM is probably defective and should be replaced |
| 10 short |
CMOS shutdown register
read/write error |
The shutdown for the CMOS
has failed |
| 11 short |
Cache error |
The L2 cache is faulty |
| 1 long, 2 short |
Failure in video system |
An error was encountered
in the video BIOS ROM, or a horizontal retrace failure has been encountered |
| 1 long, 3 short |
Memory test failure |
A fault has been detected
in memory above 64KB |
| 1 long, 8 short |
Display test failure |
The video adapter is either
missing or defective |
| 2 short |
POST Failure |
One of the hardware tests
have failed |
| 1 long |
POST has passed all tests |
|
