Intel SCB2 Product Guide - Page 92

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 Port80 codes representing the progress of the BIOS POST. Each postcode will be represented by a combination of colors from the 4 LEDs. The LEDs are in pairs of green and red. The post codes 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 11. Post Codes Post Code Diagnostic LED Decoder G=Green, R=Red, A=Amber MSB LSB 07h Off G G G 08h G Off Off Off 08h G Off Off Off 07h Off G G G 07h Off G G G 0Bh G Off G G 0Ch G G Off Off 0Eh G G G Off 0Fh G GG G 10h Off Off Off R 10h Off Off Off R 11h Off Off Off A 13h Off Off G A Description Uncompress various BIOS Modules Verify password Checksum Verify CMOS Checksum. Read Microcode updates from BIOS ROM. Initializing the processors. Set up processor registers. Select least featured processor as the BSP. Hook before the keyboard BAT command is issued. Keyboard Controller Test: The keyboard controller input buffer is free. Next, issuing the BAT command to the keyboard controller 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. Write Command Byte 8042: The initialization after the keyboard controller BAT command test is done. The keyboard command byte will be written next. Keyboard Init: The keyboard controller command byte is written. Next, issuing the pin 23 and 24 blocking and unblocking commands Disable and initialize 8259 Detect Configuration Mode, such as CMOS clear. Chipset Initialization before CMOS initialization continued 92 Intel Server Board SCB2 Product Guide