TL;DR: Does a clean install reset everything (like SMC, for example)? If not, what else should I do to be sure the computer is completely reset, like it just came from the factory?

My macbook has been acting weirdly for the past few weeks, so I decided to give it clean install with Yosemite.

I think I messed up the SMC and resetting it does not help. I have a Bootcamp partition that I used to play games. My macbook pro would get very hot while gaming on Windows, so I installed Lubbo's Fan Control. That worked for a couple days, until I realized that while booted in OSX the fans were not working at all or working full speed. I tried resetting the SMC, but that didn't help. So I installed iStat Menus, and controlled my fans manually (yeah, a lazy solution). Now I have one fan controlling app on Windows and one on OSX, and neither work as expected (in iStat when I set it to 'default' the fans stop working).

Also, I have been installing a lot of things, and leftover files are all over the place. So, now I'm getting rid of Bootcamp and clean installing Yosemite. How do I go about doing this properly and thoroughly? I'd like to make the computer fresh as it just came out of the factory. Should I do anything besides a clean install?

1 Answer 1


A fresh OS install won't reset the hardware, SMC or PRAM. It might be well worth checking both those are correctly reset before going so far as a wipe & install.

Reset the PRAM first - hold Cmd/Opt/P/R at the chimes & wait for the chimes to happen a second time.

SMC varies per machine, Mac Pro is sufficient to power off & leave the mains plug out for a minute. MacBooks are different - http://support.apple.com/kb/ht3964 covers all the variations.

Extract :

Resetting the System Management Controller (SMC)

Resetting the SMC on Mac portables with a battery you can remove

  1. Shut down the computer.
  2. Disconnect the MagSafe power adapter from the computer, if it's connected.
  3. Remove the battery.
  4. Press and hold the power button for 5 seconds.
  5. Release the power button.
  6. Reconnect the battery and MagSafe power adapter.
  7. Press the power button to turn on the computer.

Resetting the SMC on portables with a battery you should not remove on your own Note: Portable computers that have a battery you should not remove on your own include MacBook Pro (Early 2009) and later, all models of MacBook Air, and MacBook (Late 2009).

  1. Shut down the computer.
  2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
  3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
  4. Release all the keys and the power button at the same time.
  5. Press the power button to turn on the computer.

Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.

Resetting the SMC for Mac Pro, Intel-based iMac, Intel-based Mac mini, or Intel-based Xserve

  1. Shut down the computer.
  2. Unplug the computer's power cord.
  3. Wait fifteen seconds.
  4. Attach the computer's power cord.
  5. Wait five seconds, then press the power button to turn on the computer.
  • Thank you. I want to clean install anyway. Do I reset SMC and PRAM before reinstalling?
    – user96014
    Oct 17, 2014 at 14:39
  • I'd reset both & see if it fixes things on its own - just might save you the trouble. If not, then you can always repeat before or after reinstall; it won't hurt anything. Run basic drive tests too - from Recovery or booted to OS. Disk Utility, repair permissions & verify [or repair] the disk.
    – Tetsujin
    Oct 17, 2014 at 14:40

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