Sun Microsystems SPARCstation 4 110 Service Manual page 28

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 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
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
Note – If you are in the Sunmon compatibility mode (prompt is >) type n to return
to the OBP monitor (prompt is ok).
TABLE 2-1
sequence. For more detailed information about NVRAM parameters, see the
OpenBoot Command Reference.
2-4 SPARCstation 4 Model 110 Service Manual • July 1996
FIGURE 2-2
lists NVRAM parameters and explains their effect on the power-up
)