My mac seems like it is running slower and slower. While I am thinking abut installing Lion from scratch, I figure there has to be stuff I can do now to help. I have reset PR RAM recently, I have run the verify disk utility, and fixed permissions. I have seen mixed references to running a disk defragmenter. Could that help? I am on an iMac that is about 2 years old now.

I regularly run Windows XP in Parallels, Chrome, Mail.app, and iTunes.

Update: I have about 90 GB of free space. I run Onyx every month.

4 Answers 4


First, check that your processor is running full speed. Go to Preferences, Energy Saver, Options and look at the drop box down near the bottom called Processor Performance. If it is not set to "Highest", set it to that right away. This maximizes performance, but for notebooks, it may run down the battery faster. Note that not all Macs have this setting - laptops do, and my certainly my PowerMac G5 tower does, but not all Macs do.

Next, download OnyX and run the complete set of clean up and maintenance scripts and then evaluate again. Get OnyX at:


Next, you may wish to check that you have enough free space on your hard drive. Highlight the Macintosh HD icon on your desktop, CTL-click it and select Get Info from the resulting menu. Make sure you have a reasonable amount of space left. If not, a little spring cleaning may be in order.

There are two excellent apps for showing where all of your hard disk space has gone, Disk Inventory X and WhatSize. Get them at:

Disk Inventory X: http://www.derlien.com

WhatSize: http://www.id-design.com/software/whatsize

Both do a great job at letting you zero in on your largest disk space consumers, so that you can hunt down any rogue files (and both are freeware, which is good).

Finally, it is possible you may have some processes running that are consuming a lot of idle CPU, thus slowing down your machine overall. I had a bad widget that did this once. Open Activity Monitor and look at your "resting" CPU occupancy when you are not doing anything in particular with the machine. It should be pretty much zero (maybe 1% to 2% at most). If it not, identify the process or processes that are taking the time. What are they? Do you recognize them? Are they needed?

If you find one that is not needed, kill it and see how your machine starts to behave. If this is the cure, you will need to identify the startup item that launches it and delete it.

So, in summary then, take the following steps in order: 1/ Start with ensuring that your processor speed setting is full (applies to many Macs but not all) 2/ Then do Onyx based full maintenance 3/ Then check that you have sufficient available disk space 4/ Finally, search for processes that are consuming an unexpected amount of CPU

Source: http://www.mac-forums.com/forums/os-x-operating-system/80467-how-do-i-get-my-mac-run-faster.html

Another place you may find helpful:


  • "Go to Preferences, Energy Saver, Options and look at the drop box down near the bottom called Processor Performance." I don't see an options under Energy Saver. You a talking System Preferences right?
    – Mike Wills
    Jul 14, 2011 at 2:59
  • Yes, but, remember, I did get this from a forum, so it may be slightly outdated. I can further check this out when I get home.
    – Odinulf
    Jul 14, 2011 at 15:00
  • Some googling showed that this was a Leopard feature. Snow Leopard removed it. The cleanup seemed to have helped.
    – Mike Wills
    Jul 14, 2011 at 16:06

To rule in or out the need for more ram, open Activity Monitor at the end of the day and check system memory > page outs. This will show you how much data was paged out to your hard drive when ram was not available to handle it.

On my MBP with 8 Gb, I show 5.29 Gb Page ins (handled by ram) and 0 Bytes of page outs. I used to have 1 - 2 Gb of page outs before I upgraded to 8 Gb of ram.

I'm also running XP via Parallels.

  • I bought more RAM last night. I didn't realize it was so cheap right now.
    – Mike Wills
    Jul 14, 2011 at 16:07

I tried for months to analyze what was wrong with my MacBook and eventually found it went away after uninstalling Hardware Growler. Try doing without your favorite background utilities. You might find your problem is just one of them.


Regarding installing Lion from scratch, that is not actually possible, you have to have Snow Leopard installed to be able to install Lion.

EDIT: You can install Lion from scratch. When you download Lion, do not install it, instead, open the package contents, select Install ESD and from there you can burn the file as an ISO disk image. Putting this disc into the mac, rebooting while holding down the 'c' key, will boot the disc and you can format the hdd and reinstall as a clean OS.

Have you already got the maximum amount of ram your computer can handle installed? -If not I would suggest that as the first step to improving performance, especially if you're running two operating systems at once.

  • I have thought of more RAM as well. I have 4GB and can go to 8. Price may be an issue there for me right now.
    – Mike Wills
    Jul 13, 2011 at 16:30
  • 2
    that is a bogus claim. You can install Lion cleanly without having to upgrade from SL
    – Cosu
    Jul 14, 2011 at 15:05
  • I guess we'll only know when it is actually released.
    – Mike Wills
    Jul 14, 2011 at 16:05
  • Initially you would have to have Snow Leopard installed to be able to even purchase and download Lion. Apparently there will be a method of installing Lion clean, using a package called Mac First Aid, which will be available in the Lion package contents, but not sure how accurate this info is!
    – DreLambo
    Jul 14, 2011 at 16:52

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