SM240第五章读书笔记

Power on selftest

main contents:
describe the tests performed by power on self tests(POST)
identify any system failures from results presented by POST
display POST output on an ASCII display device

POST is designed to test just about everything that is internal to the system and the

system boards. POST tests the following:
CPU modules and caches
system board ASICs(DC,AC,and FHC)
busses(SBus,UPA,centerplane,boot-bus)
I/O ASICs(Sysio,FEPS,SOC)
clock board and console bus devices(NVRAM,TOD,EEPROM)
DIMMS

POST and OpenBoot work together in the system to test and manage system hardware
POST and OBP resides in the FLASHPROM on each CPU/Memory+ board. when the system is turned
on, or if a system reset is issued, POST detects and tests buses, power supplies,boards, CPUs,SIMMs, and many board functions. POST controls the status LEDs on the system front panel and all boards. POST displays diagnostic and error messages on a console terminal, if available

You can view the output from the last POST by running the show-post-results command.You can examine the report for error messages. the report generated by the show-post-results command displays a synopsis of the POST tests in a less confusing manner than the actual POST output you observed using the serial port connection

The symbols used in the show-post-results report are defined as follows:
P = present
*** = failed component
NOT = not found
0 = no failures

The following is a summary of some of the ways you can use the POST tool to assist you in diagnosing a problem:
1,POST output on ttya only
2,verbose mode depends on the NVRAM environment variable setting for diag-switch? or the system keyswitch position
3,Diagnostic complexity and depth depend on the NVRAM environment variable setting for diag-level?
4,To force POST to disable an entire board when a component fails, you must set the NVRAM environment variable configuration-policy to board
5,The disabled-board-list varible can be valuable if you want to ensure that an entire board is disabled on the next reboot

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