Gigabyte GA-P55A-UD6 User Manual page 133

POST (hex) Description
24h Prepare BIOS resource map for PCI & PnP use. If ESCD is valid, take into consider-
ation of the ESCD's legacy information
25h Early PCI initialization:
- Enumerate PCI bus number
- Assign memory & I/O resource
- Search for a valid VGA device & VGA BIOS, and put it into C000:0
26h 1. If Early_Init_Onboard_Generator is not defined Onboard clock generator initializa-
tion. Disable respective clock resource to empty PCI & DIMM slots
2. Init onboard PWM
3. Init onboard H/W monitor devices
27h Initialize INT 09 buffer
29h 1. Program CPU internal MTRR for 0-640K memory address
2. Initialize the APIC for Pentium class CPU
3. Program early chipset according to CMOS setup Example: onboard IDE controller
4. Measure CPU speed
2Bh Invoke video BIOS
2Dh 1. Initialize double-byte language font (optional)
2. Put information on screen display, including Award title, CPU type, CPU speed, full
screen logo
33h Reset keyboard if Early_Reset_KB is defined e.g. Winbond 977 series Super I/O
chips. See also POST 63h
35h Test DMA Channel 0
37h Test DMA Channel 1
39h Test DMA page registers
3Ch Test 8254
3Eh Test 8259 interrupt mask bits for channel 1
40h Test 8259 interrupt mask bits for channel 2
43h Test 8259 functionality
47h Initialize EISA slot
49h 1. Calculate total memory by testing the last double word of each 64K page
2. Program write allocation
4Eh 1. Program MTRR of M1 CPU
2. Initialize L2 cache for P6 class CPU & program CPU with proper cacheable range
3. Initialize the APIC for P6 class CPU
4. On MP platform, adjust the cacheable range to smaller one in case the cacheable
ranges between each CPU are not identical
50h Initialize USB Keyboard & Mouse
52h Test all memory (clear all extended memory to 0)
53h Clear password according to H/W jumper (optional)
55h Display number of processors (multi-processor platform)
57h 1. Display PnP logo
2. Early ISA PnP initialization
- Assign CSN to every ISA PnP device
- 133 - Appendix