Acer Altos R720 Series User Manual download pdf (Page 159)

149

Diagnostic POST code LEDs

During the system boot process, BIOS executes a number of platform

configuration processes, each of which is assigned a specific hex code

number. As each configuration routine is started, BIOS will display the

given POST code to the diagnostic POST code LEDs found on the rear of

the mainboard. 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. 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.

Diagnostic LED placement diagram

The following table lists the possible POST codes that may be displayed

on the Diagnostic POST code LEDs during system initialization.

Checkpoint

code

Diagnostic LED Decoder

Description

G=Green, R=Red, A=Amber

MSB LSB

Host Processor

0x10h OFF OFF OFF R Power-on initialization of the host

processor (bootstrap processor)

0x11h OFF OFF OFF A Host processor cache initialization

(including AP)

0x12h OFF OFF G R Starting application processor

initialization

LSB MSB

Back edge of server board

USB Port

Diagnostic LEDs

1 2 ... 154 155 156 157 158 159 160 161 162 163 164 ... 185 186

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Acer Altos R720 Series User Manual Page 159