PRAM and PMU

[mad jew]

Apple claims that a PRAM reset will automatically reset the Power Manager. I've always assumed this Power Manager to be the PMU but I've seen problems not solved with a PRAM reset yet solved with a PMU reset.

How is this so?

Any help is greatly appreciated, as ever.

 

[jane doe]

Apple claims that a PRAM reset will automatically reset the Power Manager. I've always assumed this Power Manager to be the PMU but I've seen problems not solved with a PRAM reset yet solved with a PMU reset.

How is this so?

Any help is greatly appreciated, as ever.

For most things a PRAM reset will solve. It resets a lot of the PMU settings but does not reset charge/discharge defaults.

 

[mad jew]

Hmm... Okay. Thanks for that.

Resetting the Power Manager and PRAM

Resetting the parameter RAM (PRAM) when the computer is shut down also resets the Power Manager. The following process resets both the Power Manager and the parameter RAM.

Taken from the bottom of this page, just for the record.

 

[jane doe]

Hmm... Okay. Thanks for that.





Taken from the bottom of this page, just for the record.

"Resetting the parameter RAM (PRAM) when the computer is shut down also resets the Power Manager. The following process resets both the Power Manager and the parameter RAM."

This is true for the PMU unit on the logic board but is not a full PMU reset. Resetting the PRAM does not force the battery to be polled for charge and there for does not sync the battery charge level/charge indicator.

The PMU reset will also reset the trackpad optical drive. a NVRAM reset will reset track pad, optical drive, logic board and a few other things.

On desktop units its called a SMU and does about the same thing (just no battery involved). but it does reset the computers power systems.

 

[mad jew]

Gotcha, thanks for that. I knew the rest of it, just didn't realise there were different scales of Power Manager resetting.