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Computer sound signals (IBM BIOS, AWARD BIOS, AMI BIOS, Phoenix BIOS)

Each time the computer is turned on, the POST (Power-On-Self-Test) diagnostic program is automatically started, which is "written" to the BIOS ROM.

POST checks all the important components of the computer: it monitors the working capacity of the processor, CMOS, supporting motherboard chips, and also conducts a quick test of RAM. Information on how the computer was diagnosed is given to the computer's speaker in the form of a special sound signal.

If the computer is working properly, that is, the POST diagnostic program has completed successfully, you will hear one short beep, after which the operating system will start to boot.

Upon detection of an inoperable computer component, the POST diagnostic program generates a special audio signal (a sequence of short and long beeps) that characterizes the detected error, and the computer stops operating.

If the computer has issued a sequence of short and long beeps and stopped working, you need to count the number of rings for subsequent analysis. You can turn off the computer, wait about 30 seconds and turn it on again. After counting the beeps, find your combination of sound signals in the table corresponding to the BIOS of your computer. In the tables that are presented on this page, you will find the decoding of the sound signals. Thus, even without special diagnostic tools, it is possible to localize a malfunction of the personal computer.

Because the contents of the IBM BIOS BIOS were copyrighted (that is, it could not be copied to other companies), most other computer manufacturers were forced to use ROMs from independent BIOSes. The BIOS of these independent companies was almost completely compatible with the IBM BIOS, however, the encoding of the sound signals of the diagnostic POST program for each independent manufacturer of the BIOS is different, not coincident with the encoding of the audio signals from the IBM BIOS.

Table 1. The meaning of IBM BIOS audio signals

Type of sound signal Signal strength
One short Normal completion of POST, all OK
Absent Defective power supply unit
Continuous Defective power supply unit
Repeated short Defective power supply unit
One long and one short The motherboard is defective
One signal and blank screen Defective video system
One long and two short Video system is defective (Mono / CGA)
One long and three short Video system is faulty (EGA / VGA)
Two short Defective video system (monitor not connected)
Three long The motherboard is defective (keyboard controller error)

Table 2. The value of the sound signals AWARD BIOS

Type of sound signal Signal strength
One short Normal completion of POST, all OK
Absent Defective power supply unit
One signal and blank screen Defective video system
One long and two short Defective video system
One long and three short No monitor connected
Two short Any insignificant mistake
Three long The motherboard is defective (keyboard controller error)

Table 3. The value of the AMI BIOS audio signals

Type of sound signal Signal strength
One short Normal completion of POST, all OK
Two short RAM Test Error
Three short RAM Test Error
Four short The motherboard is defective (system timer error)
Five short Faulty processor
Six short The motherboard is defective (keyboard controller error)
Seven short The motherboard is faulty (virtual mode error)
Eight short Defective video adapter or video memory test error
Nine short BIOS ROM checksum error
Ten short CMOS write / read error
Eleven short The motherboard is faulty (cache test error)
One long and three short The motherboard is faulty (extended memory error)
One long and eight short Error while testing the monitor

Table 4. The meaning of Phoenix BIOS audio signals

Type of sound signal Signal strength
1 - 1 - 3 CMOS write / read error
1 - 1 - 4 BIOS ROM checksum error
1 - 2 - 1 The motherboard is defective (system timer error)
1 - 2 - х The motherboard is defective
1 - 3 - х The motherboard is defective
1 - 4 - 1 The motherboard is defective
1 - 4 - 2 RAM Test Error
1 - 4 - 3 The motherboard is defective (system timer error)
1 - 4 - 4 An error occurred while accessing the port
2 - х - х Test error RAM (any combination that starts with two beeps)
3 - 1 - х RAM Test Error
3 - 1 - 4 The motherboard is defective
3 - 2 - 4 Defective keyboard controller
3 - 3 - 4 Defective video adapter or video memory test error
3 - 4 - х Video system defective
4 - 2 - х The motherboard is defective
4 - 3 - х The motherboard is defective
4 - 3 - 4 The motherboard is faulty (real-time clock error)
4 - 4 - 1 Serial Port Test Error
4 - 4 - 2 Parallel Port Test Error
4 - 4 - 3 Math Coprocessor Test Error


Note: x is any number from 1 to 4, if such a combination of digits is not explicitly represented.

Do not take this information as absolutely reliable. The encoding of the audio signals can change as new versions of the BIOS are released. In addition, it should be borne in mind that audio signals make it easier to pre-localize the faulty component, indicating the correct direction for further diagnosis of the computer malfunction.