The Power-on Testing variables are:
Setting diag-switch? to true causes the function diagnostic-mode? to return true. When diagnostic-mode? returns true, the system:
Performs more thorough self tests during any subsequent power-on or system reset process.
May display additional status messages (the details are implementation dependent).
Uses different configuration variables for booting. (For more details on the effects on the boot process, see Chapter 2, Booting and Testing Your System)
ok setenv diag-switch? true ok
Some systems have a hardware diagnostic switch that also cause diagnostic-mode? to return true. Such systems run the full tests at power-on and system reset if either the hardware switch is set or diag-switch? is true.
Some implementations enable you to force diag-switch? to true by using an implementation-dependent key sequence during power-on. Check your system's documentation for details, or see Appendix C, Troubleshooting Guide."
ok setenv diag-switch? false ok
When not in diagnostic mode, the system does not announce the diagnostic tests as they are performed (unless a test fails) and may perform fewer tests.