Appendix C: LED Decoder
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Intel
®
Server System H2000JF Family Service Guide
Appendix C: LED Decoder
During the system boot process, the 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, the BIOS displays the POST code to the POST Code.
Diagnostic LEDs are 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 is represented by the eight amber Diagnostic LEDs. The POST codes are divided
into two nibbles, an upper nibble and a lower nibble. The upper nibble bits are represented by
Diagnostic LEDs #4, #5, #6, #7. The lower nibble bits are represented by Diagnostics LEDs #0, #1,
#2 and #3. If the bit is set in the upper and lower nibbles, then the corresponding LED is lit. If the
bit is clear, then the corresponding LED is off.
The Diagnostic LED #7 is labeled as "MSB", and the Diagnostic LED #0 is labeled as "LSB".
In the following example, the BIOS sends a value of ACh to the diagnostic LED decoder.
A
POST Code Diagnostic LEDs
B
QSFP Activity/Link LED
Figure 90. Diagnostic LED Placement Diagram
