After I upgraded to Mountain Lion my MBP (late 2008) started to boot extremely slow. Last time it took 2 hours 46 minutes to boot, now it's already booting for 40 minutes.

I've tried cmd+r (just after restart), which brings up recovery mode; I've tried to repair the drive (via Disc Utilities), but no errors were found; I've tried to fix permissions and etc. I even tried to reinstall (not clean one, just on top).

Any of you know cause/solution to this? (Except clean reinstall, since I really don't want to do it now.)

Also, if I must clean reinstall, is it possible to do it via recovery mode? Or I must have bootable usb/cd etc?

  • Why don't you want to reinstall which will likely take you much less time than 2 hours and 46 minutes? Just to answer your question, it is possible to reinstall in recovery mode as long as you're connected to the internet. You'll have to download the OS again so it'd be much faster to install using a CD or USB. Speaking of USB, you can create a bootable copy of OSX onto a USB stick and boot to that. If it works then you can rule out your RAM being the issue.
    – Tony
    Jan 7, 2013 at 20:41

1 Answer 1


This problem may be the result of failing RAM or a failing disk drive or potentially some other hardware problem.

It should really not take more than 5 minutes to boot a mountain lion compatible Mac in the worst case.

  1. Check how much RAM OS X thinks is in the computer Apple Menu > About This Mac. Make sure it is the amount your expecting, for example if your computer when you bought or upgraded it it said it had 4GB of ram make sure its not showing that there is some different smaller number.

  2. Run a Apple Hardware Test for your Mac.

  3. Try running a memory test program, something like memtest

  4. Back up your important data

  5. Try running a disk testing program, something like TechTool Pro

If all the above fails to uncover a cause try a clean install

  1. Make sure you have a boot-able Mountain Lion Installer, etc or have an internet connection and a "OS X Internet Recovery" compatible Mac

  2. Erase the disk drive, and re-install a clean copy of OS X.

  3. Use the machine for a while, and see if the slow booting problem returns( if there is a problem with the disk the issue should return after indeterminable time). If the problem does not then this would fix it.

  4. If the problem does return I would try a different internal drive to boot the machine with, in order to determine if the problem is with the drive or with the mac.

  5. Repair / replace the failing hardware, note that parts may be covered under Apple's Warranty.

  • I've upgraded RAM to 8 gig, but this was long time ago and it was not causing any problems, this started to happen just after upgrade to ML.(btw it shows correct ram). Sep 25, 2012 at 18:41

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