Your Faster and More Stable Mac

Written by Chris Weiss (hotiron) in Tips and tricks

Call me a newbie but I only recently realized I could boot into Snow Leopard’s 64-bit kernel as the default setting when I power up my MacBook Pro.  For those of you who turn up their noses and say; “big deal,” to this, application speed tests (especially graphic apps like Photoshop) have shown that running the 64-bit OSX kernel can give you as much as a 30% performance boost with more real-world stability.
64-Bit Performance

Apple configured your modern Snow Leopard machine to boot into 32-bit mode by default because it keeps software and hardware compatibility high, which in turn lowers support calls to Cupertino.  It’s just like all the car manufactures that tune their products for the worst possible gasoline quality leaving a lot of performance “on the table” when VVT and knock sensors can take advantage of the higher octane.  The 32-bit kernel just doesn’t give you the full performance and stability that your machine is capable of and the iconpaper motto of “Stop Being Default” actually has a real performance payoff.  I especially like running in 64-bit mode now that several of my favorite apps like Photoshop, Safari, and Transmission have been tuned specifically for it.  Personally, I have not seen huge performance gains, but I have seen some especially during large, processor intensive Photoshop rendering operations.  Mostly I have seen real world stability improvements.   But who really cares about all that.  It’s 64-bit mode so it just has to be better right?  I am such a sucker for good marketing.  Mostly I just plain hate accepting someone else’s default settings.

System Profiler

So if you are running a modern Mac with Snow Leopard as many of us are, it’s easy to not only boot into 64-bit mode, but also set your machine to do it by default. The simplest way to get into 64-bit mode is as soon as you power-up your machine, just hold down the number “6” and number “4” keys at the same time until you see the Apple logo and the spinning wheel.  Then let go.  Once you get up and running, check your System Profiler/Software details and make sure it worked.  You should see “64-bit Kernel Extensions: Yes”.  You are there.  Now make sure everything is working right.  The reason you may not want to boot into 64-bit mode, especially by default, is compatibility with software drivers of various kinds.  The best way to verify all your bits and bobs work right in this mode is to simply try it.  I had a ViBook USB monitor driver that died under the 64-bit kernel but they recently released a new version that supports it so I am back in the fast lane again.

If everything is working you can set your machine to boot this way by default.  Doing this is almost as simple.  You just have to edit one line (or sometimes add a new Kernel Flags field) in your /Library/Preferences/SystemConfiguration/ folder and “” file.  FinderYou can pull down the Go menu in Finder and select Go To Folder and paste that string into the text box but I am betting you will get a tricky permission error so I highly recommend using a tool like PathFinder with it’s built in editor to change your system files. PathFinder does a great job of handling the authentication when editing system files.  Finder does not.  Once you have the file open for editing (and don’t forget the rights to save it) just insert the string “arch=x86_64” (without the quotes) into the Kernel Flags field.  Make sure you do this correctly because I once did this wrong and my machine became completely unusable.  I had to boot with my original Snow Leopard CD and open a Terminal to fix it (had to copy a working file over from my old machine via a USB drive) before I could get the machine to actually start back up again.  So like all system mods, it is tweaker beware!  Keep a bootable rescue disc with some basic OSX utilities on hand and have a current TimeMachine backup just in case.  But if you do this right then it’s sweet sailing from then onward.  I have been running like this for over 6 months and have never looked back.

Plist File

Here is a great article on 64-bit mode from the Mac Performance Guide online that will give you all the details you need. At first it can be hard to tell there is any change but after a few days of application heavy lifting you will see a difference.  And if you have been plagued with apps that terminate or the black screen of death then you very likely will see a big stability improvement. This post ought to get me seriously flamed by the real Mac cognoscenti but I’ve been running in this mode for months and it has withstood the test of time.

Your Faster and More Stable Mac, 3.5 out of 5 based on 2 ratings


  1. Jay 'Din A. says:

    Thanks for the tip. I tried running my Mac Pro at work lik this and it worked great. I noticed that my apps like Photoshop and Office started much quicker.

  2. Chris says:

    Glad it’s working out for you. I have been running in 64-bit mode by default for well over 6 months and have not had a single problem. I also noted that apps popped open faster (less bounces) and apps that would occasionally terminate unexpectedly seems to be more stable. I think it helps highly tweaked machines more than real default Macs. Just my feelings.

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