Intel SR1500AL 用户手册

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.

ACh

1

1

0

1

1

0

0

0

Result

Amber

Green

Red

Off

MSB

LSB