SMC Reset..

It is a PMU reset, with the computer off, hold down Command+Option+Power+Shift.

TEG

The computer will eventually startup, once it starts up you should be fine.

ddk121 said:

How long do I hold them down for? Is something suppose to happen with the machine?

Click to expand...

TEG said:

The computer will eventually startup, once it starts up you should be fine.

Click to expand...

That sounds misleading, as if you hold them until the machine starts up.

The correct procedure according to Apple™ is you press them down together once with the power button and let go. You then Wait 5-10 seconds and then press the power button again as normal to start up your computer.

MacRumorUser said:

That sounds misleading, as if you hold them until the machine starts up.

The correct procedure according to Apple™ is you press them down together once with the power button and let go. You then Wait 5-10 seconds and then press the power button again as normal to start up your computer.

Click to expand...

I was going with my experience with other machines, coupled with the fact that the battery was built it. I just assumed that you would hold it down, the PMU would reset/cycle, then the computer would activate.

TEG

TEG said:

I was going with my experience with other machines, coupled with the fact that the battery was built it. I just assumed that you would hold it down, the PMU would reset/cycle, then the computer would activate.

TEG

Click to expand...

Yeah they changed it for the macbook air. Normal pmu/smc reset on the macbook and macbook pro is take the battery out, press power button
Put battery back in and then power up as normal. Obviously they had to change this for the MBA.

Why not just post a link, like this?

http://docs.info.apple.com/article.html?artnum=303319

kingjr3 said:

Why not just post a link, like this?

http://docs.info.apple.com/article.html?artnum=303319

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My MBA did not restart, no display, no keyboard light and pressing the power button for long did not help either. In the end saw the link above and followed these three steps mentioned in the link and my MBA came to life and is working now.

Force Quit (Option-Command-Escape)
Restart (Control-Command-Power)
Force Shut Down (press the power button for 10 seconds)
Any issues in running the above commands?

This line in the link concerns me, how come SMC becomes unstable?
Over time, the settings in the System Management Controller may become unusable, which can result in operational anomalies with the computer.

Regards

TEG said:

It is a PMU reset, with the computer off, hold down Command+Option+Power+Shift.

TEG

Click to expand...

I don't think it has been PMU (Power Management Unit) since the PowerPC days. The first intel computers had SMU (System Management Unit) chips and the newer ones have SMC (System Management Controller)

...to the best of my knowledge.

EDIT: I guess the later Power Mac G5s were the ones with the SMU, not the first intel machines.