BIOS POST Checkpoints E-3
Table E-1 POST Checkpoint List
Checkpoint Description
74h • Serial port testing
78h • Math coprocessor testing
7Ch • Reset pointing device
80h • Set security status
84h • KB device initialization
• Set KB led upon setup requests
• Enable KB device
86h • Issue 2nd software SMI to communicate with PMU
• Enable the use of BIOS Setup, system information. and fuel gauge
6Ch • Tests and initializes FDD
Note: The FDD LED should flash once and its head should be positioned.
6Dh • password checking
88h • HDD, CD testing & parameter table setup
• Initializes HDD, CD enhanced features
90h • Displays POST status if necessary
• Changes POST mode to default text mode
94h • Initializes I/O ROM
Note: I/O ROM is an optional extension of the BIOS located on an installed add-on
card as a part of the I/O subsystem. POST detects I/O ROMs and gives them
opportunity to initialize themselves and their hardware environment.
• Shadows I/O ROM if setup requests
• Builds up free expansion ROM table
96h • Initializes PCI Card ROM
• Writes ESCD data into NVRAM
97h • Writes ESCD data into NVRAM
A0h • Initializes timer counter for DOS use
A4h • Initializes security feature
ACh • Enables NMI
• Enables parity checking
• Sets video mode
AEh • Issues 3rd software SMI to communicate with PMU
• Starts all power management timers
• Checks whether system is resumed from 0V suspend or not.
B0h • Clear memory buffer used for POST
• Select boot device
BDh • Shutdown 5
BEh • Shutdown A
BFh • Shutdown B