Stage One: Openboot Firmware And Post; Figure 2-1 Boot Prom And Scc - Sun Microsystems Sun Fire V440 Diagnostics And Troubleshooting Manual

The system controller provides access to a number of control and monitoring
functions through the ALOM command-line interface. For more information about
ALOM, see "Monitoring the System Using Sun Advanced Lights Out Manager" on
page 35.

Stage One: OpenBoot Firmware and POST

Every Sun Fire V440 server includes a chip holding about 2 Mbytes of firmware-
based code. This chip is called the boot PROM. After you turn on system power, the
first thing the system does is execute code that resides in the boot PROM.
This code, which is referred to as the OpenBoot™ firmware, is a small-scale operating
system unto itself. However, unlike a traditional operating system that can run
multiple applications for multiple simultaneous users, OpenBoot firmware runs in
single-user mode and is designed solely to configure and boot the system. OpenBoot
firmware also initiates firmware-based diagnostics that test the system, thereby
ensuring that the hardware is sufficiently "healthy" to run its normal operating
environment.
When system power is turned on, the OpenBoot firmware begins running directly
out of the boot PROM, since at this stage system memory has not been verified to
work properly.
Soon after power is turned on, the system hardware determines that at least one
CPU is powered on, and is submitting a bus access request, which indicates that the
CPU in question is at least partly functional. This becomes the master CPU, and is
responsible for executing OpenBoot firmware instructions.
The OpenBoot firmware's first actions are to check whether to run the power-on self-
test (POST) diagnostics and other tests. The POST diagnostics constitute a separate
chunk of code stored in a different area of the boot PROM (see ).
FIGURE 2-1
POST
Boot
SCC
2 Mbytes
PROM
variables
OpenBoot
firmware
Boot PROM and SCC
FIGURE 2-1
Chapter 2 Diagnostics and the Boot Process 9