Apple's 64-Bit 'Snow Leopard' OS Boots 32-Bit Kernel By Default

Thinking of upgrading your Mac to 'Snow Leopard?' At just $29 to upgrade from OS X 10.5, the answer to that is probably "yes" if you own an Apple machine. Generally speaking, early reviews have shown that the operating system is a worthy upgrade, and while it's certainly nothing revolutionary, it does offer up enough new functionality to justify the small asking price.

But not all is peachy in the world of Snow Leopard. Early testers have discovered a strange quirk within the OS that casts some doubt on just how "64-bit" the "64-bit OS" really is. While the ins and outs of the story are quite complex, the gist of it is this: Apple's OS X 10.6 boots with a 32-bit kernel by default, despite the fact that the OS can and does run 64-bit applications. Weird, right? Oh, but Snow Leopard Server boots the 64-bit kernel by default. Still with us? Good.

A product manager at Apple Australia explained that by and large, everything that users experience on a Mac will feel like 64-bit. Applications should load faster and run in a more stable fashion. In short, very few things require 64-bit mode at the kernel level, and we're guessing that it defaults to 32-bit due to the fact that a select few of the earliest Macs didn't ship with 64-bit CPUs. If you'll think way back to when Apple made the shift to Intel, some of those machines shipped with Intel's 32-bit Core Duo and Core Solo processors. Soon after, Apple made the shift to the 64-bit CPUs with the Core 2 Duo and Xeon processors. But still, Apple had to account for those early Intel iMacs, MacBooks, MacBook Pros and Mac minis with Snow Leopard; it couldn't just leave those folks hung out to dry, so it simply decided to go 32-bit at the kernel level for all Macs rather than making a fuss about it and potentially confusing the general public.

This so-called magic trick enables 32-bit-only Macs to run the whole OS and all applications in 32-bit mode, while 64-bit-capable Macs run most everything in 64-bit mode. So far as most people are concerned, they'll never notice this snafu underneath. In reality though, we don't view this as Apple being shady. In fact, they're being quite nice to consider those early Intel Mac adopters that bit the bullet before the benchmarks were even out. We're at an odd point in time with regard to 32-bit/64-bit. The world isn't quite ready to move on from the 32-bit world that we've been in for years, yet the 64-bit movement isn't large enough for Apple to neglect the 32-bit crowd.

For those with 64-bit-capable machines, there's no reason to not run the 64-bit kernel version of the OS. Thankfully, there's an odd way to make it happen, but it's pretty easy. At boot-up, just hold down the "6" and "4" keys in order to load the 64-bit kernel. Easy enough, right?  There are also a slew of free applications out there that let you select which kernel mode to run, such as Markus Winter's "Mac OS X 10.6 32-64-Bit Kernel Startup Mode Selector." If you're looking to pick up Apple's newest OS, make sure you scope out your hardware beforehand so you install the right kernel for you. Not that you'll really notice if you don't, though--or at least that's the party line from Apple.