Familiarize yourself with the system power-on initialization messages. You can then identify problems more accurately because these messages show you the types of functions the system performs at various stages of system startup. They also show the transfer of control from POST to OpenBoot to the Booter to the kernel.
The example that follows shows the OpenBoot initialization sequence in a Sun UltraTM 1 system. The messages before the banner appear on TTYA only if the diag-switch? parameter is true.
The actual OpenBoot initialization sequence is system dependent. The messages on your system may be different.
...ttya initialized ( At this point, POST has finished execution and has transferred control to OpenBoot) Probing Memory Bank #0 16 + 16 : 32 Megabytes ( Probe memory) Probing Memory Bank #1 0 + 0 : 0 Megabytes Probing Memory Bank #2 0 + 0 : 0 Megabytes Probing Memory Bank #3 0 + 0 : 0 Megabytes (If use-nvramrc? is true, the firmware executes NVRAMRC commands. The firmware then checks for Stop-x commands, and probes the devices. The Keyboard LEDs are then flashed.) Probing UPA Slot at le,0 Nothing there (Probe devices) Probing /sbus@lf,0 at 0,0 cgsix Probing /sbus@lf,0 at 1,0 Nothing there Probing /sbus@lf,0 at 2,0 Nothing there Sun Ultra 1 UPA/SBus (UltraSPARC 167 MHz), Keyboard Present (Display the banner) OpenBoot 3.0, 32 MB memory installed, Serial #7570016 Ethernet address 8:0:20:73:82:60, Host ID: 80738260. ok boot disk3 Boot device: /sbus/espdma@e,8400000/esp@e,8800000/sd@3,0 (The firmware is TFTP-ing the boot program) sd@3,0 File and args: (Control is transferred to the booter after this message is displayed) FCode UFS Reader 1.8 01 Feb 1995 17:07:00,IEEE 1275 Client Interface. (Booter starts executing) Loading: /platform/sun4u/ufsboot cpu0: SUNW,UltraSPARC (upaid 0 impl 0x0 ver 0x0 clock 143 MHz) SunOS Release 5.5 Version quick_gate_build:04/13/95 (UNIX(R) System V Release 4.0) (Control is passed to the kernel after this message is displayed) Copyright (c) 1983-1995, Sun Microsystems, Inc. (The kernel starts to execute) DEBUG enabled (More kernel messasges)