HP Vectra XE310 hp vectra xe310 series 1, technical reference manual - Page 29

BIOS Overview Order in Which POST Tests are Performed Each time the system is powered on, or a reset is performed, the POST is executed. The POST process verifies the basic functionality of the system components and initializes certain system parameters. The POST starts by displaying a graphic screen of the Hewlett-Packard logo when the PC is restarted. Devices, such as memory and newly installed hard disks, are configured automatically. The user is not requested to confirm the change. Newly removed hard disks are detected, and the user is prompted to confirm the new configuration by pressing . Note, though, that the POST does not detect when a hard disk drive has been otherwise changed. During the POST, the BIOS and other ROM data is copied into high-speed shadow RAM. The shadow RAM is addressed at the same physical location as the original ROM in a manner which is completely transparent to applications. It therefore appears to behave as very fast ROM. This technique provides faster access to the system BIOS firmware. The following table lists the POST checkpoint codes written at the start of each test. Checkpoint Code POST Routine Description 02h Verify Real Mode 03h Disable Non-Maskable Interrupt (NMI) 04h Get CPU type 06h Initialize system hardware 08h Initialize chipset with initial POST values 09h Set IN POST flag 0Ah Initialize CPU registers 0Bh Enable CPU cache 0Ch Initialize caches to initial POST values 0Eh Initialize I/O component 0Fh Initialize the local bus IDE 10h Initialize Power Management 11h Load alternate registers with initial POST values 12h Restore CPU control word during warm boot 13h Initialize PCI Bus Mastering devices 14h Initialize keyboard controller 17h Initialize cache before memory autosize 18h 8254 timer initialization 1Ah 8237 DMA controller initialization 1Ch Reset Programmable Interrupt Controller 24h Set ES segment register to 4 GB 26h Enable A20 line 28h Autosize DRAM 29h Initialize POST Memory Manager 2Ah Clear 512 KB base RAM 25