Intel® Server System S9200WK Product Family Setup and Service Guide
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Appendix D.
POST Code Diagnostic LED Decoder
As an aid to assist in troubleshooting a system hang that occurs
during a system’s Power
-On Self-Test
(POST) process, the server board includes a blank of eight POST Code Diagnostic LEDs on the back edge of
the server board as shown in the Figure below.
Figure 87. POST diagnostic LED identification
During the system boot process, Memory Reference Code (MRC) and System BIOS execute a number of
memory initialization and platform configuration processes, each of which is assigned a specific hex POST
code number.
As each routine is started, the given POST code number is displayed to the POST Code Diagnostic LEDs on
the back edge of the server board.
During a POST system hang, the displayed post code can be used to identify the last POST routine that was
run prior to the error occurring, helping to isolate the possible cause of the hang condition.
Each POST code is represented by eight LEDs; four green and four amber. The POST codes are divided into
two nibbles, an upper nibble and a lower nibble. The upper nibble bits are represented by Amber Diagnostic
LEDs and the lower nibble bits are represented by Green Diagnostics LEDs. If the bit is set in the upper and
lower nibbles, the corresponding LED is lit. If the bit is clear, the corresponding LED is off.
Note:
Diagnostic LEDs are best read and decoded when viewing the LEDs from the front of the system.
In the following example, the BIOS sends a value of ACh to the diagnostic LED decoder. The LEDs are
decoded as shown in Table 2.
Table 2. POST progress code LED example
Binary Value
LED State
Upper Nibble AMBER LEDs
Lower Nibble GREEN LEDs
MSB
LSB
1
0
1
0
1
1
0
0
ON
OFF
ON
OFF
ON
ON
OFF
OFF
Hex Value
8h
4h
2h
1h
8h
4h
2h
1h
Hex Result
Ah
Ch
