ADLINK Express-LPC - Manual (Page 73)

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9 BIOS Checkpoints, Beep Codes
This section of this document lists checkpoints and beep codes generated by AMIBIOS. The
checkpoints defined in this document are inherent to the AMIBIOS generic core, and do not
include any chipset or board specific checkpoint definitions.
Checkpoints and Beep Codes Definition
A checkpoint is either a byte or word value output to I/O port 80h. The BIOS outputs checkpoints
throughout bootblock and Power-On Self Test (POST) to indicate the task the system is currently
executing. Checkpoints are very useful for debugging problems that occur during the preboot process.
Beep codes are used by the BIOS to indicate a serious or fatal error. They are used when an error
occurs before the system video has been initialized, and generated by the system board speaker.
Viewing BIOS Checkpoints
Viewing all checkpoints generated by the BIOS requires a checkpoint card, also referred to as a
“POST Card” or “POST Diagnostic Card”. These are ISA or PCI add-in cards that show the value
of I/O port 80h on a LED display.
Some computers display checkpoints in the bottom right corner of the screen during POST. This
display method is limited, since it only displays checkpoints that occur after the video card has
been activated.
Keep in mind that not all computers using AMIBIOS enable this feature. In most cases, a
checkpoint card is the best tool for viewing AMIBIOS checkpoints.