•  Shawn
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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 Mar[censored] 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.

I don't see this as a big issue. Most people that need the 64 bit kernel are going to know how to enable it, while those that need 32 bit my not.


My Mac is 64-bit capable but I'm glad Apple chose to start a 32-bit kernel by default. Applications like Parallels Deskop and Vmware Fusion both do not work with the 64-bit kernel at this time. I think Apple was wise to be on the cautious side until the rest of the companies catch up.


"In reality though, we don't view this as Apple being shady."

Sorry, but I have to disagree. Apple has long promoted its intel systems as being 64-bit capable. Those planning for the future purchased accordingly. Imagine those thousands of people realizing they were hosed by Apple (if not outright defrauded), with a 32-bit capable processor instead?

Whether they need it not is a paternalistic viewpoint: people don't need iPods, so it's okay to ship them Zunes? Simple fact is this: people are entitled to get what they paid for. If Apple made even the indirect promise of 64-bit then it is responsible for providing it--not some cobbled together, shady workaround.


Agreed Alvin, this move makes sense to me as well, though it's incumbent upon Apple to be as transparent about it as possible.


To quote someone from another forum:


I think there's a technical disconnect here.

If you boot into a 64bit kernel, none of your 32bit device drivers will work, so people who are upgrading will struggle. Drivers built for snow leopard will have both 32 & 64 bit code, but until that happens, booting into 64bit by default isn't the right way to go.

That said, 'booting into 64bit' only refers to the kernel. All of the other libraries that apps depend on, AppKit, FoundationKit, libc, etc are all 64 bit, and will load if a 64 bit processor is accessible. Also, any program that was compiled with 64bit code will run in 64bits period, giving you that (2x) improvement.

The biggest problem for users will be that their software (Photoshop, Logic, etc) will be 64 bit, but their plugins might not be. If any program has plugins or extensions that are not 64 bit, it will have to be relaunched into 32bit mode to use them. Contrary to contentcreator's comments, OSX does not 'grind a bit' when loading 64 bit code, nor does it load BOTH 32 and 64 bit. It loads 64bit code if it's dependent libraries and the processor support it. If not, it degrades gracefully (and speedily) to 32bit code.

That said, nearly all programs 32/64/ppc continue to run well on SL, and all of them get to take advantage of GCD when they run, so they run a bit faster as well.

In the pre-release versions of SL, all of the Macbook Pros, Mac Pros and XServes could be set to boot in 64bit by default (without 32bit device drivers), and the others (with the exception of the MBA and Mini) could be booted with the '64' keys held down. I guess they removed it to keep users from getting confused if their devices stopped working. My guess it will be the default for all machines once the driver community has moved all of their code over.


Thanks for the insight Bryan. One word that comes to mind in situations like this is "transparency". Apple is marketing SL as a 64-bit OS, so they have to be careful to educate folks what that means, the way you have here actually, otherwise people get pretty twitchy about being mislead.


I mostly just care that it works well. For 29 bucks it was an inexpensive buy in to get it and it installed easily for me with no burps, hiccups, or farts.

I had no issues with programs although my needs are few. I run MS Office, Aperture, Toast, and Handbrake mostly. I have allot of movies backed up onto a drive and can watch them with the Mac if I want to.

All in all it works for me. The 4GB RAM ceiling is OK with me because my Mac only has and can handle 4GB anyway.

Apple should have been more up front about the way it loads a 32bit kernel by default, but I'll get over it.