Resetting the PMU (exact directions)

Hi,

Reset the power manager by simultaneously pressing and then releasing Shift-Control-Option-Power on the keyboard. If you have the Clock preferences set to automatically set the time you won't see any evidence that it has been reset if you connect to the internet when restarting
John

You press all of the keys at once.
The computer won't start if done correctly.

John

Here's the exact manual reference:
"Reset the power manager by pressing the key combination Control-Option-Shift-power.
Warning: Make sure you do not hold down the "fn" key when resetting the power manager.
Warning: Resetting the power manager means you will means you will also need to reset the date and time (using the Date & Time control panel)."
Richard

And yes, it is the power button.

No, it's not necessary to do it more than once.

When the PRAM is reset (command-option-p-r) you hold that combination while starting and release them after you hear the startup chime three times.

John

Could someone offer a succinct explanation of what kind of circumstances call for resetting each of these?

Under OS 9 and before, it seemed like restarting and rebuilding the desktop took care of 90% of the quirks and glitches. Are these ROUGHLY ANALOGOUS to that, in their own specific ways?

Thanks,
cb


iBook G4, iMac Intel Duo Core Mac OS X (10.4.8)

From an Apple KB article http://docs.info.apple.com/article.html?artnum=14449 :

The Power Manager is an integrated circuit (computer chip) that is usually on the logic board of the PowerBook and iBook. As the name implies, it is responsible for power management of the computer. It controls backlighting, hard disk spin down, sleep and wake, some charging aspects, trackpad control, and some input/output as it relates to the computer sleeping.

Over time, the settings in the Power Manager may become unusable, which can result in operational anomalies with the computer. Examples include not turning on, not waking from sleep, not charging the battery, or not seeing the AC Adapter, among others.

Resetting the PMU is not intended for resolution of a stall or situation in which the computer is unresponsive. A PMU reset should not be necessary except as a last resort in cases where a hardware failure of the power management system is suspected.

The Power Manager is an integrated circuit (computer chip) that is usually on the logic board of the PowerBook and iBook. As the name implies, it is responsible for power management of the computer. It controls backlighting, hard disk spin down, sleep and wake, some charging aspects, trackpad control, and some input/output as it relates to the computer sleeping.

Over time, the settings in the Power Manager may become unusable, which can result in operational anomalies with the computer. Examples include not turning on, not waking from sleep, not charging the battery, or not seeing the AC Adapter, among others.

Resetting the PMU is not intended for resolution of a stall or situation in which the computer is unresponsive. A PMU reset should not be necessary except as a last resort in cases where a hardware failure of the power management system is suspected.

No, it isn't analogous to rebuilding the Desktop in OS 9. Resetting the PMU isn't necessary in most cases. If you don't get a low battery warning or it won't charge you reset the PMU. There are other settings that can be reset with keyboard commands or via open firmware such as the PRAM and NVRAM.

John

Thanks, JH, for the info. Sorry I can't throw a star your way since it's not my post, but FWIW I do appreciate the input!

You're welcome.