2-4 SPARCstation 5 Service Manual—November 1996
2
2.2 After Power Is Switched On
When you turn on the system power, the low-level POST phase is initiated
if any of the following circumstances apply:
• diag-switch? NVRAM parameter is set to true.
• Stop-d keys are held down when you turn on the power.
• Keyboard is disconnected, and diag-switch? is set to false.
The low-level POST code, which is stored in the boot PROM, is designed to test
the most basic functions of the system hardware. The status of the POST is
conveyed by four LEDs on the Sun™ Type-4, Type-5, and Compact 1
keyboards. The Caps Lock LED blinks to indicate that the tests are in progress.
If a failure is detected during low-level POST, one of the other three LEDs will
light to indicate the nature of the failure. See Chapter 3, “Power-On Self-Test
(POST),” for more information.
Note – You can skip the POST phase by turning on the system while holding
down the Stop key.
At the successful completion of the low-level POST phase, the OpenBoot
PROM firmware takes control and performs the following initialization
sequence:
• Initialize system
• Probe memory, then CPU
• Evaluate Script (if use-nvramrc? is set to true)
• Probe SBus devices and interpret their drivers
• Install the console (see Figure 2-2)
After initialization, a system banner appears on the screen, and the high-level
testing begins. When the high-level tests are finished, the system checks
parameters stored in the NVRAM to determine the next step. Depending on
the following parameter settings, the system will:
• Boot the operating system from a specified location, if auto-boot?
is set to true
• Suppress the boot sequence and enter the FORTH Monitor (ok prompt),
if auto-boot? is set to false
• Continually cycle through the OpenBoot PROM sequence, if mfg-switch?
is set to true
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