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Appendix C: POST Code Diagnostic LEDs

Intel

® Server Board S5000PAL / S5000XAL TPS

Revision 1.7

Intel order number: D31979-010

100

Appendix C: POST Code Diagnostic LED Decoder

During the system boot process, BIOS executes a number of platform configuration processes, each of

which is assigned a specific hex POST code number. As each configuration routine is started, BIOS will

display the given POST code to the POST Code Diagnostic LEDs found on the back edge of the server

board. To assist in troubleshooting a system hang during the POST process, the Diagnostic LEDs can

be used to identify the last POST process to be executed.

Each POST code will be represented by a combination of colors from the four LEDs. The LEDs are

capable of displaying three colors: green, red, and amber. The POST codes are divided into two nibbles,

an upper nibble and a lower nibble. Each bit in the upper nibble is represented by a red LED and each bit

in the lower nibble is represented by a green LED. If both bits are set in the upper and lower nibbles then

both red and green LEDs are lit, resulting in an amber color. If both bits are clear, then the LED is off.

In the below example, BIOS sends a value of ACh to the diagnostic LED decoder. The LEDs are decoded

as follows:

•

red bits = 1010b = Ah

green bits = 1100b = Ch

Since the red bits correspond to the upper nibble and the green bits correspond to the lower nibble, the

two are concatenated to be ACh.

Table 44: POST Progress Code LED Example

LEDs

Red

Green

Red

Green

Red

Green

Red

Green

ACh

Result

Amber

Green

Red

Off

MSB

LSB

Figure 28. Diagnostic LED Placement Diagram

LSB

MSB

Diagnostic LEDs

Back edge of baseboard

USB Port

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