Listed below are the BEEP codes associated with the POST of several BIOS manufacturers. BEEP codes are generated PRIOR to the verification of the basic I/O functions required to display an error message/code on the display screen. BEEP codes are ALWAYS hardware related and not caused by software.
In order for the PC to display basic information on the screen the following functions need to be operational. If a failure occurs before the PC has determined that it can display information on the screen it announces the failure(s) via BEEP codes thru the PC speaker. This allows you to determine the basic failure symptom that cannot be displayed graphically.
1. Power supply must exit the power on state, detect PWR OK and release its reset signal.
2. CPU must exit the reset state and be able to execute instructions.
3. BIOS chip must be accessible for reading data.
4. BIOS checksum must be compared. (Valid data in BIOS)
5. CMOS must be accessible for reading data.
6. CMOS checksum must be compared. (Valid data in CMOS)
7. CPU must be able to access memory. (Memory controller, mem bus, mem module)
8. First 64KB of memory must be operational and able to read/write valid data to store POST code.
9. I/O bus must be accessible. (I/O controller)
10. I/O bus must be able to write/read data to the video subsystem. (graphics PCB)
These operations are not necessarily performed in the order listed. Nor are they the only tests performed in POST but these basic functions must be performed to determine if the system is able to display error data on the screen during higher level tests before the system confirms that it can boot from the FDD/HDD.
NOTE!! The cache memory controller is generally enabled after the POST is complete. Cache memory problems are SELDOM if ever detected during the POST sequence.
General BIOS info from WIM's BIOS page
1 beep - DRAM refresh failure
2 beeps - Parity Circuit Failure
3 beeps - Base 64K RAM failure
4 beeps - System Timer Failure
5 beeps - Processor Failure
6 beeps - Keyboard Controller / Gate A20 Failure
7 beeps - Virtual Mode Exception Error
8 beeps - Display Memory Read/Write Failure
9 beeps - ROM BIOS Checksum Failure
10 beeps - CMOS Shutdown Register Read/Write Error
For 1 beep, 2 beeps, or 3 beeps try reseating the memory first. If the error still occurs, replace the memory with known good chips/SIMM's.
For 4 beeps, 5 beeps, 7 beeps, or 10 beeps the system board must be sent in for repair.
For 6 beeps try reseating the keyboard controller chip. If the error still occurs, replace the keyboard chip.
If the error persists, check parts of the system relating to the keyboard, e.g. try another keyboard, check to see if the system has a keyboard fuse.
8 beeps indicates a memory error on the video adapter. Replace the video card or the memory on the video card.
9 beeps indicates faulty BIOS chip(s). It is not likely that this error can be corrected by reseating the chips.
Consult the motherboard supplier or an AMI product distributor for replacement part(s).
If no beeps are heard and no display is on the screen, The first thing to check is the power supply. Connect a LED to the POWER LED connection on the motherboard. If this LED lights and the drive(s) spin up then the power supply will usually be good. Next, inspect the motherboard for loose components. A loose or missing CPU, BIOS chip, Crystal Oscillator, or Chipset chip will cause the motherboard not to function.
Next, eliminate the possibility of interference by a bad or improperly set up I/O card by removing all card except the video adapter.
The system should at least power up and wait for a drive time-out. Insert the cards back into the system one at a time until the problem happens again. When the system does nothing, the problem will be with the last expansion card that was put in.
If the above suggestions fail to cause any change in the dysfunction of the system, the motherboard must be returned for repair.
Beep - Currently the only beep code indicates that a video error has occurred and the BIOS cannot initialize the video screen to display any additional information. This beep code consists of a single long beep followed by two short beeps. Any other beeps are probably a RAM problem.
1-1-3 CMOS write/read failure.
1-1-4 BIOS ROM checksum error.
1-2-1 System timer failure. (Programmable Interval Timer PIT)
1-2-2 DMA (direct Memory Access) failure.
1-2-3 DMA page register failure.
1-3-1 RAM refresh failure.
1-3-3 64K RAM chip or data line failure.
1-3-4 64K RAM odd/even logic failure.
1-4-1 64K RAM address line failure.
1-4-2 64K RAM parity error.
2-?-? Any beep series starting with 2 beeps indicates a 64K RAM chip or data line error.
3-1-1 Master DMA register test.
3-1-2 Mslave DMA register failure.
3-1-3 Master interrupt mask register failure.
3-1-4 Slave interrupt mask register failure.
3-2-4 Keyboard controller failure.
3-3-4 Screen (video) memory failure.
3-4-1 Screen initialization failure.
3-4-2 Screen retrace failure.
4-2-1 Timer tick interrupt test failure.
4-2-2 Shutdown test failure.
4-2-4 Unexpected interrupt in protected mode.
4-3-1 RAM test failure above address 0FFFFh (64K +)
4-3-3 Interval timer channel 2 test failure.
4-3-4 Time of day clock failure.
4-4-1 Serial port test failure.
4-4-2 Parallel port test failure.
4-4-3 Math Co-processor failure.
BEEP codes may vary dependent upon the revision of BIOS. This list is for reference only.
Phoenix BIOS codes in PDF format from Phoenix's page.
Phoenix BIOS FAQ and info page from Phoenix's site.