7.3 How to Use POST Diagnostics

When you turn on the system power, POST diagnostics run automatically if any of the following conditions apply:

• The OpenBoot PROM variable diag-switch? is set to true when you power on the system.

• You hold down the keyboard's Stop and D keys as you power on the system.

7.3.1 Before You Begin

You can view POST diagnostic and error messages locally on an attached terminal.

To view POST diagnostic and error messages on the local system, you need to connect an alphanumeric terminal or establish a tip connection to another Sun system. For more information, see "2.10 About Communicating With the Server" or if you already have a console setup, see "7.4 How to Set Up a tip Connection".

You must verify baud rates between a system and a monitor or a system and a terminal. See "7.4.1 How to Verify the Baud Rate".

You can choose to run an abbreviated POST with concise error and status reporting or run an extensive POST with more detailed messages. For more information, see "7.7 How to Set the Diagnostic Level for POST and OBDiag".

If a console or a monitor is not connected to serial port A (default port) of a system to be tested, the keyboard LEDs are used to determine error conditions. See "7.12.1 Error Indications".

7.3.2 What to Do

Ensure that the front panel keyswitch is in the Standby position.

You can initialize POST one of two ways:

• By setting the diag-switch? to true and the diag-level to max or min, followed by power cycling the system unit

• By simultaneously pressing the keyboard Stop and D keys while power is applied to the system unit

To set the diag-switch? to true and power cycle the system unit:

1. When the ok prompt is displayed, type the following command:

   ok setenv diag-switch? true

2. At the Type-5 keyboard, power cycle the system by simultaneously pressing the Shift key and the Power-on key After a few seconds press the Power-on key again, or press the Power button on the system once.

The keyswitch must be set to the Power-On/Off position.

The system runs the POST diagnostics. POST displays status and error messages on the system console. For more information, see the "Results" section below.

Upon successful completion of POST, the system runs OBDiag. For more information about OBDiag, see "7.5 About OpenBoot Diagnostics (OBDiag)" and "7.6 How to Use OpenBoot Diagnostics (OBDiag)".

7.3.3 Results

While POST is running, you can observe its progress and any error indications in the following locations:

• System console or through a tip connection

• Front panel fault LEDs

• Keyboard LEDs (if a keyboard is present)

7.3.3.1 Observing POST in Progress

As POST runs, it displays detailed diagnostic status messages on the system console. If POST detects an error, it displays an error message on the system console that indicates the failing part. A sample error message is provided below:

Power On Self Test Failed. Cause: DIMM U0702 or System Board
ok

POST status and error conditions are indicated by the general fault LED on the system front panel. The LED flashes slowly to indicate that POST is running. It remains lit if POST detects a fault.

If a Sun Type-5 keyboard is attached, POST status and error indications are also displayed via the four LEDs on the keyboard. When POST starts, all four keyboard LEDs flash on and off simultaneously. After that, the Caps Lock LED flashes slowly to indicate POST is running. If an error is detected, the pattern of the lit LEDs provides an error indication. See "7.12.1 Error Indications" for more information.

If POST detects an error condition that prevents the system from booting, it halts operation and displays the ok prompt. The last message displayed by POST prior to the ok prompt indicates which part you need to replace.