4-4 CHAPTER 4
APPENDIX A: POST CODES
ISA POST codes are typically output to port address 80h.
01-02
C0
03
04
05
06
07
C1
C5
08
09
0A
0B
POST(hex)
DESCRIPTION
Reserved.
Turn off OEM specific cache, shadow.
1.Initialize EISA registers (EISA BIOS only).
2.Initialize all the standard devices with default values Standard devices includes.
-DMA controller (8237).
-Programmable Interrupt Controller (8259).
-Programmable Interval Timer (8254).
-RTC chip.
Reserved
1.Keyboard Controller Self-Test.
2.Enable Keyboard Interface.
Reserved.
Verifies CMOS's basic R/W functionality.
Auto-detection of onboard DRAM & Cache.
Copy the BIOS from ROM into E0000-FFFFF shadow RAM so that POST will
go faster.
Test the first 256K DRAM.
OEM specific cache initialization. (if needed)
1.Initialize the first 32 interrupt vectors with corresponding Interrupt handlers
Initialize INT no from 33-120 with Dummy (Suprious)
Interrupt Handler.
2.Issue CPUID instruction to identify CPU type.
3.Early Power Management initialization. (OEM specific)
1.Verify the RTC time is valid or not.
2.Detect bad battery.
3.Read CMOS data into BIOS stack area.
4.PnP initializations including. (PnP BIOS only)
-Assign CSN to PnP ISA card.
-Create resource map from ESCD.
5.Assign IO & Memory for PCI devices. (PCI BIOS only)
