MacBook Pro’s 2009-2010 | Default to 32 bit Kernel

While studying some Apple info I came across a little tidbit about the default OS kernel being 32 bit versus 64 bit on 2009-2010 models.¬¨‚Ć I had assumed that with Snow Leopard and with the 64 bit capable processors Intel Core 2 Duo’s that the default had moved to 64 bit on machines 2009+.¬¨‚Ć This turns out to not be the case, only MacBook Pro 2011 models default to the 64 bit kernel, previous models in 2009 and 2010 can run the 64 bit kernel but you must first make a change to the boot.plist file to make the change permanent.

To see if you are running the 64 bit kernel extensions go to About this Mac and look.¬† Click on the Software Overview Column on the left then take a look Рyou can see my 2010 MacBook Pro was set to No.

sudo systemsetup -setkernelbootarchitecture x86_64

To change use these extensions you can type one command in terminal to make the change permanent.

You can also simply test the 64 bit kernel by rebooting your machine and as soon as you see the grey screen hold down the 6 and the 4 keys simultaneously.  (Can Boot 32 mode by restarting and holding 3 and the 2 keys).  This change will only hold until the next restart.  The terminal command above make the change permanent.

Why change? Well if you are running 4 GB or more of RAM the 64 bit kernel is needed to properly access the memory (despite Apple computers utizling RAM differently than Windows OS this still hold true for the most part).¬† With Apple hardware moving to the 64 bit kernel by default with 2011 + models looks like Apple is going full 64bit from here on.¬†¬† Will you see any major performance gains Рnot really major but running 10.6.8 with the 64 bit kernel does seem to be slightly faster on my machine.

(After the change)