Intel SR1690WB - Server System - 0 MB RAM, Service Manual

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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 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 that was 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. Given the bit is set in the upper and lower nibbles,
then corresponding LED is lit. If the bit is clear, corresponding LED is off.
The Diagnostic LED #7 is labeled as “MSB”, and the Diagnostic LED #0 is labeled with
“LSB”.
Figure 53. Diagnostic LED Placement Diagram
Table 9. POST Progress Code LED Example
LEDs
Upper Nibble LEDs Lower Nibble LEDs
MSB LSB
LED
#7
LED
#6
LED
#5
LED
#4
LED
#3
LED
#2
LED
#1
LED
#0
AF003321
POST LED 7
POST LED 6
POST LED 5
POST LED 4 POST LED 0
POST LED 1
POST LED 2
POST LED 3