Specifications

Power Mac G5 Troubleshooting - 5
General Information
Resetting the Logic Board
Many system problems can be resolved by resetting the logic board. Because the Power
Mac G5 (Late 2004) uses a System Management Unit (SMU) controller chip rather than a
Power Management Unit (PMU) controller chip, the logic board does not include a reset
button. Instead, to reset the logic board, do the following:
1. Shut down the computer.
2. Unplug the computer from its power source.
3. Wait 15 seconds.
4. Plug the power cord back in, and turn the computer on. If the computer does not
power on, there is something else wrong with it; refer to the “Startup Failures” section
of “Symptom Charts” in this chapter.
Note: The above procedure resets the computer’s PRAM. After resetting the logic board,
be sure to reset the time, date, and other system parameter settings.
RAM and Processor Verification: Power-On Self Test
A power-on self test in the computer’s ROM automatically runs whenever the computer is
started up after being fully shut down (the test does not run if the computer is only
restarted). If the test detects a problem, the status LED located above the power button on
the front of the computer will flash in the following ways*:
• 1 Flash: No RAM is installed or detected.
• 2 Flashes: Incompatible RAM types are installed.
• 3 Flashes: No RAM banks passed memory testing.
• 4 Flashes: No good boot images are detected in the boot ROM (and/or there is a bad
sys config block).
• 5 Flashes: The processor is not usable.
* Note: The status LED lights up when the power button is depressed at startup. Do not
count this light as one of the diagnostic flashes.