Mac OS 10.6 Snow Leopard and 64-bit computing, revised 02/14/10

A lot of noise has been made over the switch to 64-bit computing lately -- especially now that many manufacturers are bundling their computers with 64-bit versions of Windows Vista and 7 with their machines. This changeover was long overdue, as most desktop computers have been 64-bit capable for about five years now.

The move to 64-bit architecture is important because it allows computers to process twice as much data at any given time while also giving them the ability to use more memory.

For Mac aficionados, 64-bit computing has come in the form of Mac OS 10.6 Snow Leopard -- if, that is, you know how to fully enable it.

Last night I discovered that Apple enables the 32-bit kernel by default on any machine other than a Mac server. The kernel, as defined by Wikipedia, is the central component of most computer operating systems. It acts as a bridge between applications and the actual data processing done at the hardware level.

The funny thing is that I made this discovery in a very round-about way: I was installing Windows 7 with BootCamp and VMWare Fusion. I had purchased Fusion v2 several months ago and was checking to see what updates I would need to install to make it run properly with Snow Leopard. The folks over at VMWare wrote up a nice article about the two kernels on their site.

Oddly enough, all of the built-in applications and any 64-bit programs you install will run in 64-bit mode with the 32-bit kernel and extensions enabled. Apple claims that the user will experience the benefits of 64-bit computing, even though at its core a computer not configured to run in 64-bit mode will still be a 32-bit machine.

So how do you enable the 64-bit kernel?

First, start by verifying which version of the kernel you have enabled. You can do this by opening the System Profiler.

You'll notice that that I have enabled the 64-bit kernel in the field 64-bit Kernel and Extensions. If the 32-bit kernel is enabled you'll see the words 64-bit Kernel and Extensions: No.

Chances are you're not using a Mac Xserve server, so the likelihood is that you have the 32-bit kernel enabled.

The simplest way to enable the 64-bit kernel is to hold down the "6" and "4" keys when starting your machine. Unfortunately, if you use this method, the 64-bit kernel will not be permanently enabled and you'll be forced to do this each time you start your computer.

If you're UNIX command-line savvy, you can enable the 64-bit kernel by making changes to a particular text configuration file and restarting your computer. You can find detailed instructions on how to do that here.

If you're like me and prefer to have a nice GUI interface to work with, you can use a program such as the free K64 Enabler application.



K64 can be downloaded here.