Sun Microsystems Sun Fire V440 Diagnostics And Troubleshooting Manual page 28

The extent of these power-on self-tests, and whether they are performed at all, is
controlled by configuration variables stored in the removable system configuration
card (SCC). These OpenBoot configuration variables are discussed in "Controlling
POST Diagnostics" on page 13.
As soon as POST diagnostics can verify that some subset of system memory is
functional, tests are loaded into system memory.
The Purpose of POST Diagnostics
The POST diagnostics verify the core functionality of the system. A successful
execution of the POST diagnostics does not ensure that there is nothing wrong with
the server, but it does ensure that the server can proceed to the next stage of the boot
process.
For a Sun Fire V440 server, this means:
At least one of the CPUs is working.
At least a subset (512 Mbytes) of system memory is functional.
Input/output bridges located on the motherboard are functioning.
The PCI bus is intact—that is, there are no electrical shorts.
It is possible for a system to pass all POST diagnostics and still be unable to boot the
operating system. However, you can run POST diagnostics even when a system fails
to boot, and these tests are likely to disclose the source of most hardware problems.
POST generally reports errors that are persistent in nature. To catch intermittent
problems, consider running a system exercising tool. See "About Exercising the
System" on page 39.
What POST Diagnostics Do
Each POST diagnostic is a low-level test designed to pinpoint faults in a specific
hardware component. For example, individual memory tests called address bitwalk
and data bitwalk ensure that binary 0s and 1s can be written on each address and data
line. During such a test, the POST may display output similar to this example.
1>Data Bitwalk on Slave 3
1>
In this example, CPU 1 is the master CPU, as indicated by the prompt 1>, and it is
about to test the memory associated with CPU 3, as indicated by the message
"Slave 3."
10 Sun Fire V440 Server Diagnostics and Troubleshooting Guide • July 2003
Test Bank 0.