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Chapter 2 NAS Head 2-31
FIGURE 2-7 Examples of POST LED Coding
During the POST process, each light sequence represents a specific Port-80 POST
code. If a system should hang during POST, the diagnostic LEDs present the last test
executed before the hang. When you read the LEDs, observe them from the back of
the system. The most significant bit (MSB) is the leftmost LED, and the least
significant bit (LSB) is the rightmost LED.
Note – When comparing a diagnostic LED color sequence from the server Main
Board to those listed in the diagnostic LED decoder in the following tables, the LEDs
on the Main Board should be referenced when viewed by looking into the system
from the back. Reading the LEDs from left to right, the most-significant bit is located
on the left.
TABLE 2-15 Boot Block POST Progress LED Code Table (Port 80h Codes)
POST
Code
Diagnostic LED Decoder
(G = green, R = red, A = amber) Description
MSB LSB
MSB LSB
10h Off Off Off R The NMI is disabled. Start power-on delay. Initialization code
checksum verified.
11h Off Off Off A Initialize the DMA controller, perform the keyboard controller BAT
test, start memory refresh, and enter 4 GB flat mode.
AMBER
RED
GREEN OFF
OFF
AMBER
RED GREEN
1 0 0 1 0 0 1 1
POST Code = 95h
upper nibble = 1001 = 9h
lower nibble = 0101 = 5h
POST Code = CAh
upper nibble = 1100 = Ch
lower nibble = 1010 = Ah
1 1 1 0 0 1 0 0
POST LEDs (as viewed from back of server)
= upper nibble bits
= lower nibble bits
high bits
(on left)
high bits
(on left)
low bits
(on right)
low bits
(on right)