
POST code checkpoints
The following table shows the checkpoints, LED codes, and task description of events that may occur during the POST portion of the BIOS:
Check | Diagnostic LED decoder | Description | |||
point | G=Green, R=Red, O=Orange |
| |||
|
|
|
|
|
|
03 | Off | Off | G | G | Disable NMI, Parity, video for EGA, and DMA controllers. Initialize |
|
|
|
|
| BIOS, POST, Runtime data area. Also initialize BIOS modules |
|
|
|
|
| on POST entry and GPNV area. Initialized CMOS as mentioned |
|
|
|
|
| in the Kernel Variable “wCMOSFlags.” |
|
|
|
|
|
|
04 | Off | G | Off | Off | Check CMOS diagnostic byte to determine if battery power is OK |
|
|
|
|
| and CMOS checksum is OK. Verify CMOS checksum manually |
|
|
|
|
| by reading storage area. If the CMOS checksum is bad, update |
|
|
|
|
| CMOS with |
|
|
|
|
| Initialize status register A. |
|
|
|
|
| Initialize data variables that are based on CMOS setup |
|
|
|
|
| questions. Initialize both the 8259 compatible PICs in the system. |
|
|
|
|
|
|
05 | Off | G | Off | G | Initialize the interrupt controller in hardware (generally PIC) and |
|
|
|
|
| interrupt vector table. |
|
|
|
|
|
|
06 | Off | G | G | Off | Do R/W test to |
|
|
|
|
| Install the POSTINT1Ch handler. Enable |
|
|
|
|
| timer interrupt. |
|
|
|
|
| Trap INT1Ch vector to “POSTINT1ChHandlerBlock.” |
|
|
|
|
|
|
08 | G | Off | Off | Off | Initialize the CPU. The BAT test is being done on KBC. The |
|
|
|
|
| keyboard controller command byte is being programmed after |
|
|
|
|
| Auto detection of KB/MS using AMI |
|
|
|
|
|
|
C0 | R | R | Off | Off | Early CPU Init Start — Disable Cache - Init Local APIC |
|
|
|
|
|
|
C1 | R | R | Off | G | Set up boot strap processor information. |
|
|
|
|
|
|
C2 | R | R | G | Off | Set up boot strap processor for POST. |
|
|
|
|
|
|
C5 | R | O | Off | G | Enumerate and set up application processors. |
|
|
|
|
|
|
C6 | R | O | G | Off | |
|
|
|
|
|
|
C7 | R | O | G | G | Early CPU Init Exit. |
|
|
|
|
|
|
0A | G | Off | G | Off | Initialize the 8042 compatible keyboard controller. |
|
|
|
|
|
|
0B | G | Off | G | G | Detect the presence of PS/2 mouse. |
|
|
|
|
|
|
0C | G | G | Off | Off | Detect the presence of keyboard in KBC port. |
|
|
|
|
|
|
128 | www.gateway.com |