Magic Startup Key Combinations Saved Me From a Clean Install

by Matthew Russell

Since doing an "unclean" install of Tiger back in April, I've noticed that I have intermittent troubles with my PowerBook coming out of sleep. Often times, my machine just appears completely unresponsive, gives me a solemn black screen, and I have to hold down the power button to force a shut down, and then boot back up -- not fun.

A colleague's solution to the problem was to do a clean install, and come to think of it, I've received that same advice from a lot of folks involving a variety of problems. It appears that a clean install is standard practice for many folks in the Mac community -- but not me. Although it may be pragmatic and I should probably just go with it, I just can't; it seems so inadequate to me. I don't want to back all of my stuff up, I don't want to degunk my Mac by zapping everything and starting all over, and I don't want to think that the health of my machine depends upon doing one of the things that I disliked so much about Windows. Call me stubborn (or stupid), but my plan is to do complete backups regularly to my external drive, and not ever do a clean install unless absolutely forced into it by some sort of unresolvable failure.

But getting back to the magic key combination -- it turns out that my power problems have resolved now that I reset my PowerBook G4’s Power Management Unit (PMU). I just followed these instructions, which directed me to hold down shift-ctrl-option-power for 5 seconds while my machine was off, wait five seconds, and then do a normal start up. After some extensive testing, I have concluded that my power problems have indeed been vanquished, and I now have one less reason to do a clean install! (And since we're at it, I also resolved a weird issue with XCode last night that was threatening me into making a clean image or a clean install. As indicated in the comments, the fix was to switch to the Universal SDK instead of the default setting even though my intention was not to build a universal binary. I still don’t understand it, but it works. Hooray!)

For your edification, the following links may be of use to you if you’re interested in escaping a clean install or want to demystify some of the “magic” that happens when you call Apple Care:

Am I the only one who refuses to do a clean install?


Sgt. Wilson
2006-02-06 16:44:29
You can do a clean install without zapping all the 3rd party stuff... in the installer, choose "Clean Install (preserve user & network settings)" - or some such. The only things that get the axe are the /System folder (and I think the /Developer folder)... and the old /System folder is now within "/Previous Systems"... works like a charm for me. You literally log in after the restart and everything is back where you were expecting it. Also, if there was somehow something that got installed in /System prior to the upgrade, that you still need (unlikely), just go into "/Previous Systems" to retrieve it.

Of course remember after a month or so of healthy use to remove the "/Previous Systems" folder else you're sacrificing a few GBs of disk space.

2006-02-06 17:22:51
If you do a bit of a web search you'll find all sorts of people have this problem with both PowerBooks and iBooks waking from sleep for apparently no reason and going into a hang state. The processor is usually peaked and the fan is running on high. The only way out is to restart.

The problem will stop if you turn off wifi, but why would you want to do that? All the same, I plug in a network cable when using my iBook at home so it won't have this problem in the middle of the night.

This problem has been around for at least a year and Apple either doesn't know about it, won't acknowledge it. Whichever it is, they haven't fixed it obviously.

2006-02-06 17:32:00
@Matt : My fan is never running on high, or running at all for that matter, and my machine doesn't come out of sleep involuntarily. It's when I try to open the lid to wake it from sleep that it hangs on me, but still -- I'd be interested to know if resetting the PMU helps this at all?
2006-02-06 17:33:55
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2006-02-06 18:14:36
Same issue with my wife's powerbook: the computer is stuck with a black screen, and the computer little light is not "breathing" like you get when sleeping, and no fan, no hard drive activity. But the computer is not off, because you can't just switch it on by pressing the power button. You first have to switch it off by pressing the power button for several secs (note there is no way to tell when it is finally off, but we usually keep it pushed and count to 10).

I have to try this little trick. Will report on it. Thanks, Matt!

2006-02-06 18:18:55
@Joker: Thanks for pointing out that garbage that was prefixed to the links (issue with cutting/pasting a "fancy" double quote instead of the standard plain vanilla one). Fixed the links.
Anonymous Coward
2006-02-06 18:56:01
I too have recovered from some really strange problems by clean installing. I've had such great success that now when I purchase a new Mac, the first thing i do is put a clean system on it.

Glad to hear you got that one figured out. Here's hoping you won't see other issues raise their ugly heads as time goes on, as I have.

A few of the myriad of upgrade-related problems I have encountered have to do with Unix file ownership & permission issues resulting from various OS upgrades; and some of the problems are just so looney they are nearly impossible to track down without devoting a large number of hours to debugging the system. After spending entire weekends trying to figure some of the worst ones out, I came to the conclusion that I simply am not willing to part with the time it would take to deal with them! So I always do a clean install first thing when i set up a Mac for myself, friends, or family.

Note that you can also reset the PMU in PPC Macs by pressing the Kudo switch (

2006-02-07 00:21:48
Please note, there is no such thing as a clean install. Erase and Install, Archive and Install often are both confused for clean install. For purpose of clarity, please read my above website to understand the differences and edit your own article so it is clear what type of install you are doing.
2006-02-07 02:49:35
@gopher: Thanks for taking the time to for "please read my above website to understand the differences and edit your own article", I really don't think it's that complicated. Technically speaking, you're absolutely right, but as far as I'm concerned, there's an "unclean install" (anything that's not what you have listed as an "erase and install") and an clean install (what you call an "erase and install").

Don't you think If you hear people say "Clean Install" about Mac OS X, please correct them as that is not the term Apple uses for Mac OS X installation. is taking the issue...well...a bit too far?

Thanks for the intel.

2006-02-07 03:39:18
I second gopher's comments. When I hear "clean install," I'm never sure what the person means. "Erase and Install" is pretty clear, as is "Archive and Install," the latter almost always being all that is needed (and quite easy to do). It may seem pedantic to you to follow Apple's terminology, but it really makes things clearer. Maybe this is because Windows does not have an Archive and Install option? (Don't know; I rarely use Windows.)
Dan Rempel
2006-02-08 07:24:44
I'll stick my neck out and suggest that OS re-installations are a windoze-driven superstition. OS X is a *nix-based system, and it's really difficult (although not impossible) to completely hose it. It might take some time to track down a problem, and some people may choose to simply re-install rather than take that time, but in my experience it's rarely necessary.


2006-02-08 19:11:04
I agree with Dan that the whole concept of clean installs (which for what its worth is a descriptive enough term for me) originate from the realm of windoze. I do think though that there's nothing quite as refreshing as a clean/erase install on my powerbook, although it needs to happen far less often than windoze. I upgraded to Tiger because it was fast/easy to do, and for the most part it was fine, maybe its a psychological thing that makes me reload...
Small Paul
2006-03-02 05:25:45
I'd agree that clean installs are superstition, in that we who do them don't know why they work, but for us newbs, they can be the quickest way to solve problems.

We just don't have the time or brain-power to actually track down the cause of whatever's plaguing us. For good or ill, computers are a mass-market product now, and Macs are specifically marketed as such. All computer problems can be tracked down, but some of us just want to get on with our simple computing tasks, and if a clean install is the quickest way, we'll do it.