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72 Chapter 4
23h 1. Check validity of RTC value:
e.g. a value of 5Ah is an invalid value for RTC minute.
2. Load CMOS settings into BIOS stack. If CMOS checksum fails, use default
value instead.
3. Prepare BIOS resource map for PCI & PnP use. If ESCD is valid, take into
consideration of the ESCD’s legacy information.
4. Onboard clock generator initialization. Disable respective clock resource to
empty PCI & DIMM slots.
5. Early PCI initialization
-Enumerate PCI bus number
-Assign memory & I/O resource
-Search for a valid VGA device and VGA BIOS, and put it into C000:0
24h Reserved
25h Reserved
26h Reserved
27h Initialize INT 09 buffer
28h Reserved
29h 1. Program CPU internal MTRR (P6 & PII) 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.
5. Invoke video BIOS.
2Ah Reserved
2Bh Reserved
2Ch Reserved
2Dh 1. Initialize multi-language
2. Put information on screen display, including Award title, CPU type, CPU
speed.
2Eh Reserved
2Fh Reserved
30h Reserved
31h Reserved
32h Reserved
33h Reset keyboard except Win bond 977 series Super I/O chips.
34h Reserved
35h Reserved
36h Reserved
37h Reserved
38h Reserved
39h Reserved
3Ah Reserved
3Bh Reserved
3Ch Test 8254.
3Dh Reserved
3Eh Test 8259 interrupt mask bits for channel 1
Checkpoint Description