Appendix B: Post Code Diagnostic Led Decoder; Figure 22. Diagnostic Led Placement Diagram Example; Table 29: Post Progress Code Led Example - Intel SR1530CLR - Server System - 0 MB RAM Technical Specification, Installation And Operation Manual

Appendix B: POST Code Diagnostic LED Decoder

Appendix B: POST Code Diagnostic LED Decoder
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.
8h
LEDs Red
ACh 1
Result Amber
MSB
USB Port
USB Port
Back edge of baseboard

Figure 22. Diagnostic LED Placement Diagram Example

42

Table 29: POST Progress Code LED Example

4h
Green Red Green
1 0 1
Green
Diagnostic LEDs
MSB
Intel order number D71005-005
Intel® Server Systems SR1530CL/SR1530HCL/SR1530HCS
and SR1530CLR/SR1530HCLR/SR1530HCLSR
2h
Red Green
1 0
Red
LSB
1h
Red Green
0 0
Off
LSB
Revision 2.2