Diagnostic Leds; Table 21. Post Codes - IBM @server xSeries 343 Product Manual

Diagnostic LEDs

To help diagnose POST failures, a set of four bi-color diagnostic LEDs is located on the back edge
of the baseboard. Each of the four LEDs can have one of four states: Off, Green, Red, or Amber.
The LED diagnostics feature consists of a hardware decoder and four dual color LEDs. During
POST, the LEDs will display all normal Port-80 codes representing the progress of the BIOS
POST. Each POST code will be represented by a combination of colors from the four LEDs. The
LEDs are in pairs of green and red. The post codes are broken into two nibbles, an upper 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 nibble then both
red and green LEDs are lit, resulting in an amber color. Likewise, if both bits are clear then the red
and green LEDs are off.
During the POST process, each light sequence represents a specific Port-80 POST code. If a
system should hang during POST, the diagnostic LEDs will present the last test executed before the
hang. When reading the lights, the LEDs should be observed from the back of the system. The
most significant bit (MSB) is the first LED on the left, and the least significant bit (LSB) is the last
LED on the right.
NOTE
When comparing a diagnostic LED color string from the baseboard to those
listed in the diagnostic LED decoder in the following tables, the LEDs on the
baseboard should be referenced when viewed by looking into the system from
the back. Reading the LEDs from left to right, the Hi bit is located on the left.
Table 21. POST Codes
Diagnostic LED Decoder
Post
G=Green, R=Red, A=Amber
Code
MSB
07h Off
08h G
08h G
07h Off
07h Off
0Bh G
0Ch G
0Eh G
xSeries 343 Product Guide
LSB Description
G G G Uncompress various BIOS Modules.
Off Off Off Verify password Checksum.
Off Off Off Verify CMOS Checksum.
G G G Read Microcode updates from BIOS ROM.
G G G Initializing the processors. Set up processor registers. Select least
featured processor as the boot strap processor (BSP).
Off G G Hook before the keyboard BAT command is issued.
G Off Off Keyboard Controller Test: The keyboard controller input buffer is
free. Next, issuing the BAT command to the keyboard controller.
G G Off Init after Keyboard Test: The keyboard controller BAT command
result has been verified. Next, performing any necessary
initialization after the keyboard controller BAT command test.
69