BIOS Beep Codes
Whenever a recoverable error occurs during POST, the BIOS displays
an error message describing the problem. The BIOS also
issues a beep code (one long tone followed by two short tones) during
POST if the video configuration fails (a faulty video card or no card
installed) or if an external ROM module does not properly checksum to
zero.
An external ROM module (for example, a video BIOS) can also issue
audible errors, usually consisting of one long tone followed by a
series of short tones. For more information on the beep codes issued,
check the documentation for that external device.
There are several POST routines that issue a POST terminal error
and shut down the system if they fail. Before shutting down the
system, the terminal-error handler issues a beep code signifying the
test point error, writes the error to I/O port 80h, attempts to
initialize the video and writes the error in the upper left corner of
the screen (using both monochrome and color adapters).
If POST completes normally, the BIOS issues one short beep before
passing control to the operating system.
I hope this helps.
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