Intel S1200RP Service Guide - Page 162

Appendix C: LED Decoder 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 a sequence of 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, and #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". Figure 108. Diagnostic LED Placement Diagram The LEDs are decoded as follows. Table 10. POST Progress Code LED Example LEDs Status Decode Result MSB LED #7 8h ON 1 Ah Upper Nibble AMBER LEDs 7 6 5 LED #6 LED #5 LED #4 4h 2h 1h OFF ON OFF 0 1 0 4 LED #3 8h ON 1 Ch Lower Nibble GREEN LEDs 3 2 LSB LED #2 LED #1 LED #0 4h 2h 1h ON OFF OFF 1 0 0 150 Intel® Server System R1000RP Service Guide