Intel S7200AP - Table 9. POST Progress Code Decoding LED Example

NOTE: All POST Diagnostic codes must be read from left to right starting from MSB to LSB in given
numerical order (7-6-5-4-3-2-1-0) when user is facing the back of the system as shown in Error!
Reference source not found.
. Failing to follow this instruction will result on a wrong
interpretation.
In the following example, the BIOS sends a value of ACh to the diagnostic LED decoder.
The LEDs are decoded as follows:
Table 9. POST Progress Code Decoding LED Example
LEDs
Upper Nibble AMBER LEDs
Lower Nibble GREEN LEDs
MSB
LSB
LED #7
LED #6
LED #5
LED #4
LED #3
LED #2
LED #1
LED #0
8h
4h
2h
1h
8h
4h
2h
1h
Status
ON
OFF
ON
OFF
ON
ON
OFF
OFF
Results
1
0
1
0
1
1
0
0
Ah
Ch
Upper nibble bits = 1010b = Ah; Lower nibble bits = 1100b = Ch; the two are concatenated as ACh
Early POST Memory Initialization MRC Diagnostic Codes
Memory Initialization at the beginning of POST includes multiple functions, including: discovery, channel
training, validation that the DIMM population is acceptable and functional, initialization of the IMC and
other hardware settings, and initialization of applicable RAS configurations.
Below is a brief list of the Diagnostic LED codes displayed during memory initialization by the Memory
Reference Code (MRC), the BIOS component responsible for it. There are two types of POST Diagnostic
Codes used by the MRC, Fatal Error Codes and Progress Codes.
MRC Fatal Error Codes are necessary because if the Memory Initialization fails badly for some reason – like
no usable memory installed – the system would not have the resources to give any other error indication.
So in the case of a major failure during Memory Initialization, the system outputs a Fatal Error Code to Port
80 (the Diagnostic LEDs) and executes a Halt. These Fatal Error Halts do not change the System Status LED,
and they do not get logged as SEL Events.
The MRC Progress Codes are displays to the Diagnostic LEDs that show the execution point in the MRC
operational path at each step. The intent is that if the system hangs during execution of the MRC, the LED
display will tell at what point in the code the system was executing.
Be aware that these are Diagnostic LED display codes used in early POST by the MRC. Later in POST, these
same Diagnostic LED display codes are used for other BIOS Progress Codes.
Also, MRC Fatal Error Codes and MRC Progress Codes are not controlled by the BIOS and are subject to
change based upon changes implemented in the memory reference code.