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Diagnostic LEDs

Troubleshooting

The BIOS sends a 1-byte hex code to port 80 prior to each POST task. These codes are displayed on eight orange LEDs, located on the system board and available at the back of the server chassis. They can provide troubleshooting information in the event of a system hang during POST.

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 Description point

03Disable 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.”

04Check 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 power-on default values and clear passwords. Initialize status register A.

Initialize data variables that are based on CMOS setup questions. Initialize both the 8259 compatible PICs in the system.

05Initialize the interrupt controller in hardware (generally PIC) and interrupt vector table.

06Do R/W test to CH-2 count reg. Initialize CH-0 as system timer. Install the POSTINT1Ch handler. Enable IRQ-0 in PIC for system timer interrupt. Trap INT1Ch vector to “POSTINT1ChHandlerBlock.”

08Initialize 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 KB-5.

C0 Early CPU Init Start — Disable Cache - Init Local APIC

C1 Set up boot strap processor information.

C2 Set up boot strap processor for POST.

C5 Enumerate and set up application processors.

C6 Re-enable cache for boot strap processor.

C7 Early CPU Init Exit.

0A Initialize the 8042 compatible keyboard controller.

0B Detect the presence of PS/2 mouse.

0C Detect the presence of keyboard in KBC port.

0E Testing and initialization of different input devices. Also, update the Kernel Variables.

Trap the INT09h vector, so that the POST INT09h handler gets control for IRQ1. Uncompress all available language, BIOS logo, and Silent logo modules.

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