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The computer POST (Power On Self Test) ensures that it meets the basic computer requirements and the hardware is working appropriately before the boot process begins. If the computer passes the POST, the computer continues to start in a normal mode. However, if the computer fails the POST, the computer emits a series of LED codes during the start-up. The system LED is integrated on the Power button.
The following table shows different light patterns and what they indicate.
Amber LED state | White LED state | System state | Notes |
---|---|---|---|
Off | Off | S4, S5 |
|
Off | Blinking | S1, S3 | System is in a low power state, either S1 or S3. This does not indicate a fault condition. |
Previous State | Previous State | S3, no PWRGD_PS | This entry provides for the possibility of a delay from SLP_S3# active to PWRGD_PS inactive. |
Blinking | Off | S0, no PWRGD_PS | Boot Failure - The computer is receiving electrical power, and power supplied by the power supply is normal. A device might be malfunctioning or incorrectly installed. Refer to the table below for Amber Blinking Pattern diagnostics suggestion and possible failures. |
Steady | Off | S0, no PWRGD_PS, Code fetch = 0 | Boot Failure - This is a system fault error condition, including the power supply. Only the +5VSB rail on the power supply is working correctly. |
Off | Steady | S0, no PWRGD_PS, Code fetch = 1 | This indicates that the host BIOS has started to execute and the LED register is now writable. |
Amber LED state | White LED state | System state | Notes |
---|---|---|---|
2 | 1 | Bad MBD | Bad MBD - Rows A, G, H, and J from table 12.4 of SIO Spec - Pre-Post indicators [40] |
2 | 2 | Bad MB, PSU or cabling | Bad MBD, PSU or PSU cabling - Rows B, C and D of table 12.4 SIO spec [40] |
2 | 3 | Bad MBD, DIMMS, or CPU | Bad MBD, DIMMS or CPU - Rows F and K from table 12.4 of SIO spec [40] |
2 | 4 | Bad coin cell | Bad coin cell - Row M of table 12.4 in SIO spec [40] |
Amber LED state | White LED state | System state | Notes |
---|---|---|---|
2 | 5 | BIOS state 1 | BIOS Post code (Old LED pattern 0001) Corrupt BIOS. |
2 | 6 | BIOS state 2 | BIOS Post code (Old LED pattern 0010) CPU config or CPU failure. |
2 | 7 | BIOS state 3 | BIOS Post code (Old LED pattern 0011) MEM config in process. Appropriate mem modules detected but failure has occurred. |
3 | 1 | BIOS state 4 | BIOS Post code (Old LED pattern 0100) Combine PCI device config or failure with video sub sytem config or failure. BIOS to eliminate 0101 video code. |
3 | 2 | BIOS state 5 | BIOS Post code (Old LED pattern 0110) Combine storage and USB config or failure. BIOS to eliminate 0111 USB code. |
3 | 3 | BIOS state 6 | BIOS Post code (Old LED pattern 1000) MEM config, no memory detected. |
3 | 4 | BIOS state 7 | BIOS Post code (Old LED pattern 1001) Fatal Motherboard error. |
3 | 5 | BIOS state 8 | BIOS Post code (Old LED pattern 1010) Mem config, modules incompatible or invalid config. |
3 | 6 | BIOS state 9 | BIOS Post code (Old LED pattern 1011) combine "Other pre-video activity and resource configuration codes. BIOS to eliminate 1100 code. |
3 | 7 | BIOS state 10 | BIOS Post code (Old LED pattern 1110) Other pre-post activity, routine subsequent to video init. |