Power Mac G5: The lights are on but no one's home

The recent ice storm that crippled New England and left me looking for other shelter seemed to have killed my 2005 Power Mac G5. The night of the ice storm the lights in the house blinked off, then on, then off again... They stayed off for four days, along with the furnace, until the power company put my town back on line.

A week later, when I attempted to start the G5 in my home office the main power light came on, and stayed on when ever it was plugged in, and the desktop would not begin the boot sequence, nor were any sounds emitted such as the fans starting up.

With lots of other things to take care of I delayed troubleshooting it, but thought that it would eventually require a trip to the Apple Store Genius Bar for a drop off. Today I finally did a search and came up with this little wonder:

How to reset the SMU on a Power Mac G5

The SMU (System Management Unit) is a microcontroller chip on the logic board that controls all power functions for your computer. If your computer is experiencing any issues regarding these functions, resetting the SMU may resolve the issue. The functions controlled by the SMU include:

* It tells the computer when to turn on, turn off, sleep, wake, idle, and so on.
* It handles system resets from various commands.
* It controls the fan.

The guts circuit board did not look the same as in the photo on their article, so I started pushing all the transistors and every little silvery bumps I could find. Close to my RAM memory slots, I finally found a tiny, round, silver button on a small black square base that was in fact slightly pushable.

Upon reassembling the tower's side door and re-inserting all the cables, I was very happy to hear that little whir of the fan as the computer took its first breath after being resuscitated. The prospect of waiting in line at the Apple Store during Christmas week was something I was not looking forward to.

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