Beep codes are a series of beeps through the speaker that indicate
a problem during POST (Power On Self Test).  If text appears on
the video screen, the motherboard has completed POST; any other tone
from the speaker indicates something other than a POST error.  These
tones are not described in the following table.

The beep error codes are all a series of three sets of beeps.  The 
duration of the beep tones are constant, but the length of the pauses
between the beeps varies.  For example, a 1-3-3 beep code will sound
like one beep, a pause, three beeps run together, another pause, and
then three more beeps run together.

There is one beep code that is often misunderstood.  With no video card
installed, or if the video card is failing, the motherboard will
generate a long-short-long-short beep code.  This is often misinterpreted
as a 1-2-1 beep code, but POST errors always vary the length of the pause,
and not the duration of the beep tone.

Another way of identifying a POST error is to use a device called a
POST-card.  This peripheral card is inserted into one of the ISA slots
and has an LED (or LCD) read-out showing the contents of port 80h.



Beep	Port  
code	80h	Description

1-1-3	02h	CMOS write/read failure
1-1-4	03h	ROM BIOS checksum failure
1-2-1	04h	Programmable interval timer failure
1-2-2	05h	DMA initialization failure
1-2-3	06h	DMA page register write/read failure
1-3-1	08h	RAM refresh verification failure
1-3-3	0Ah	First 64k RAM chip or data line failure, multi-bit
1-3-4	0Bh	First 64k RAM odd/even logic failure
1-4-1	0Ch	Address line failure first 64k RAM
1-4-2	0Dh	Parity failure first 64k RAM
2-1-1	10h	Bit 0 first 64k RAM failure
2-1-2	11h	Bit 1 first 64k RAM failure
2-1-3	12h	Bit 2 first 64k RAM failure
2-1-4	13h	Bit 3 first 64k RAM failure
2-2-1	14h	Bit 4 first 64k RAM failure
2-2-2	15h	Bit 5 first 64k RAM failure
2-2-3	16h	Bit 6 first 64k RAM failure
2-2-4	17h	Bit 7 first 64k RAM failure
2-3-1	18h	Bit 8 first 64k RAM failure
2-3-2	19h	Bit 9 first 64k RAM failure
2-3-3	1Ah	Bit 10 first 64k RAM failure
2-3-4	1Bh	Bit 11 first 64k RAM failure
2-4-1	1Ch	Bit 12 first 64k RAM failure
2-4-2	1Dh	Bit 13 first 64k RAM failure
2-4-3	1Eh	Bit 14 first 64k RAM failure
2-4-4	1Fh	Bit 15 first 64k RAM failure
3-1-1	20h	Slave DMA register failure
3-1-2	21h	Master DMA register failure
3-1-3	22h	Master interrupt mask register failure
3-1-4	23h	Slave interrupt mask register failure
3-2-4	27h	Keyboard controller test failure
3-3-4	2Bh	Screen initialization failure
3-4-1	2Ch	Screen retrace test failure
3-4-2	2Dh	Search for video ROM in progress
4-2-1	34h	Timer tick interrupt test in progress or failure
4-2-2	35h	Shutdown test in progress or failure
4-2-3	36h	Gate A20 failure
4-2-4	37h	Unexpected interrupt in protected mode
4-3-1	38h	RAM test in progress or address failure > FFFFh
4-3-3	3Ah	Interval timer channel 2 test or failure
4-3-4	3Bh	Time-of-day clock test or failure
4-4-1	3Ch	Serial port test or failure
4-4-2	3Dh	Parallel port test or failure
4-4-3	3Eh	Math coprocessor test or failure