1. Open Terminal
2. As I mentioned in the article, No 64-Bit Snow Leopard Kernel For You!, only Macs with 64-bit EFI firmware will run Snow Leopard’s kernel in 64-bit mode out of the box. Check if your system is compatible by typing the following command

   ioreg -l -p IODeviceTree | grep firmware-abi

3. If it says “EFI64″, your system is capable of easily booting into 64-bit Snow Leopard. Otherwise, you need to go looking for a more-complicated method.
4. You can test this capability by rebooting and holding down the “6″ and “4″ keys through the grey Apple screen. Check System Profiler (in the “Software” section) to see if you’re running a 64-bit kernel.
5. Now let’s set the kernel configuration files to boot in 64-bit mode by default. Type the following command from Terminal (you’ll need to enter your password when prompted):

   sudo defaults write \

   /Library/Preferences/SystemConfiguration/com.apple.Boot \

   'Kernel Flags' 'arch=x86_64'

6. Finally, let’s set the NVRAM to boot in 64-bit mode as well. Type this command:

   sudo nvram boot-args="arch=x86_64"

7. Now you’re set. Your system will always boot in 64-bit mode. To get it to run 32-bit, just hold “3″ and “2″ through the Apple screen on reboot.

That’s it! You’ve now got a 64-bit Mac!

My iMac now boots in 64-bit mode by default!

© sfoskett for Stephen Foskett, Pack Rat, 2010. | How To Boot Snow Leopard in 64-Bit Mode
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The Snow Leopard kernel refuses to boot in 64-bit mode on most Macs. Should you care?

There is clearly a ton of interest in Mac OS X 10.6, Snow Leopard: My Snow Leopard features hardware compatibility chart had over 20,000 visitors in just three days! But one chart element is generating an inordinate amount of interest: Whether or not Snow Leopard can boot in 64-bit mode.

Snow Leopard is a solid but visually unremarkable update to Apple’s OS X family. Although there are many new technical features, it’s not loaded with flash. In fact, even experienced Mac users would be hard-pressed to notice that their system had even been updated!

As I mentioned in that post, I was most-interested in the potential to use Grand Central Dispatch and OpenCL to accelerate my system’s performance. Both features are supported on most Macs built over the last year or two, and they create a great foundation for future development. QuickTime X is interesting as well, though only Nvidia 9400M-based Macs (like my 2009 Mini) support it’s hardware-accelerated H.264 capabilities. The fact that so much of the operating system has been re-written using these modern capabilities is probably the biggest Snow Leopard feature.

Snow Leopard Does Not Boot 64-Bit…

I wasn’t all that concerned about whether the OS X kernel booted in 32-bit or 64-bit mode, but was intrigued to find that Snow Leopard boots with a 32-bit kernel on every Mac other than the rack-mount Xserve.

Much pre-launch discussion revolved around whether or not a given system was even capable of booting in 64-bit mode. There are three critical elements that determine whether a given machine will boot a 64-bit Snow Leopard kernel:

1. All system hardware must have 64-bit drivers, including the CPU, chipset, and peripheral chips. The 64-bit kernel exclusively uses 64-bit kexts (drivers), and these are rarer than the 32-bit ones used by Leopard.
2. It must use 64-bit EFI (firmware). Even though EFI32 can technically boot a 64-bit operating system just fine, Apple will not allow this. Only Macs made over the last few years include EFI64.
3. Apple must allow the system to boot in 64-bit mode. This is the most confusing. Many Macs will not boot Snow Leopard in 64-bit mode even though they are brand new, have no unusual hardware, and include EFI64. This includes all non-Pro MacBooks and Mac Minis.

So there you have it. No matter what you do, Snow Leopard will not boot with a 64-bit kernel and kexts on the majority of Macs. One could understand if there was a lack of drivers or some other technical limitation, as is the case with older Macs, the but this is not the case for the latest MacBook and Mac Mini systems. They won’t boot with a 64-bit kernel because the kernel refuses to boot.

The only Mac model that boots with a 64-bit kernel by default is the 2008 and 2009 Xserve (Xserve2,1 and Xserve3,1) running Snow Leopard Server. The following Macs can boot in 64-bit mode in non-server Snow Leopard if you hold down the 6 and 4 keys on boot or if you modify your “/Library/Preferences/SystemConfiguration/com.apple.Boot.plist” file as described at Netkas:

If your Mac is not included in this list, you will not be able to boot Snow Leopard in 64-bit mode. MacBook and Mac Mini models definitely will not boot into 64-bit Snow Leopard. The later Unibody MacBook Pros (5,3 and 5,4) are not listed, and it is not known if they work or not.

…But Why Do You Care?

Why do enthusiasts care so much about the “bitness” of their hardware and software? Geeks have been arguing over the merits of “bigger-bits” for decades. I remember Mac users claiming PCs were inferior because Macs used true 16-bit Motorola CPUs while PCs were stuck with an 8-bit bus. The gaming world did much to foster 64-bit mania, with Atari claiming their Jaguar was the first 64-bit console, and Nintendo even naming theirs the “N64″. But does it really matter?

In theory, a 64-bit operating system should make most-effective use of 64-bit CPUs, increasing performance and maximum addressable RAM. In the case of Intel CPUs, there are many improvements when running the 64-bit (x64) instruction set instead of legacy 32-bit (IA-32) mode. So, from a hardware perspective, 64 bits is definitely superior.

But Mac OS X can run 64-bit applications regardless of the bitness of the kernel. I am writing this post in 64-bit Safari running on a 32-bit Snow Leopard kernel. Many of the applications I normally run are 64-bit in Snow Leopard, including Safari, Mail, and the Finder. This last is important: All Snow Leopard users get a speedy 64-bit ground-up rewrite of Finder, which is their main operating system experience.

32-bit Snow Leopard runs 64-bit versions of many applications, including Safari, QuickTime X, iCal, Mail, and the Finder itself. Notable 32-bit apps include Microsoft Office, iTunes, and iPhoto.

Therefore, regardless of which kernel mode you have booted into, many of your daily activities will use full 64-bit applications. 64-bit versions of iTunes, iPhoto, and Microsoft Office might be nice, but they’re the exception not the rule, and I expect to see these move up to 64-bit soon.

Why do so many Macs not use the 64-bit version of Snow Leopard? One reason is compatibility: The 64-bit kernel requires a full set of 64-bit drivers, and these may have been lacking at launch. Another reason might be that these systems would not see much benefit from running a 64-bit operating system since they are limited to 4 GB of RAM. I would not be at all surprised if later point-revisions of OS X 10.6 enable booting in 64-bit mode by default, at least for the machines listed above and newer models. Those of us with older machines (like this MacBookPro3,1) might never see it, though.

I should note that there are a few 64-bit features lacking in 32-bit Snow Leopard. But some applications, including VMware Fusion, will not run at all under a 64-bit Snow Leopard kernel. And there is the question of driver compatibility. I am not an Apple apologist or fanboy, but I do use Macs 100% of the time for business and pleasure. I think it stinks that Apple now lags behind Microsoft in the race to provide a 64-bit desktop operating system. But the decision is understandable and it has little impact on the daily lives of end users.

© sfoskett for Stephen Foskett, Pack Rat, 2009. | No 64-Bit Snow Leopard Kernel For You!
This post was categorized as Apple, Computer History. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.

Mac OS X 10.6 "Snow Leopard" deliveries begin on August 28!

Although Apple’s web site clearly states that Snow Leopard “Delivers on August 28th,” it is unclear if other sources will be so punctual. We definitely expect Apple Stores to have plenty of stock on Friday morning, but what of Amazon.com pre-orders? Will they also deliver on Friday, or will those of us who pre-ordered there have to wait a few days for this undercover upgrade?

Who Gets What

Snow Leopard is really a major jump forward in terms of advanced hardware and software integration. It brings Grand Central, OpenCL, full 64-bit mode, and QuickTime X along with Exchange support and many tweaks. But many of these features are highly hardware-dependent, so not all Mac users will get everything.

Here’s a cheat sheet I put together based on Apple’s documentation:

This table is based on the following facts:

1. Snow Leopard only supports Intel-based Macs. PowerPC Macs need not apply.
2. Booting Snow Leopard in 64-bit mode requires 64-bit EFI, and many pre-2007 Macs have only a 32-bit EFI. You can check your Mac (and help me fix my table) by typing “ioreg -l -p IODeviceTree | grep firmware-abi” in a Terminal window. If it says “EFI64″, your system is capable of running 64-bit Snow Leopard (though it can still run 64-bit apps). But Snow Leopard defaults to 32-bit mode on ALL Macs other than the Xserve at this point, and no one is sure why!
3. Grand Central Dispatch requires a multi-core CPU. This eliminates the original base-model 2006 Mac Mini, since it used a single-core CPU.
4. OpenCL requires newer Nvidia or the ATI graphics chips. This leaves out many pre-2008 models and some iMac and Mac Pro configurations. Check Apple’s list if you’re not sure.
5. QuickTime H.264 Hardware Acceleration only works with the Nvidia 9400M chipset. This leaves out many pre-2008 machines and even the latest Mac Pros, though they probably have enough horsepower on their own.

Finally, if you’re excited about the new Microsoft Exchange support in Mail.app, iCal, and the Address Book be warned! In order for any of this to work, your server must be running Microsoft Exchange Server 2007 Service Pack 1 Update Rollup 4. And most companies still aren’t updated that far!

Update: Check my follow-up post on 64-bit Snow Leopard for more about this controversial aspect!

I’m Updating!

I held off on Amazon and placed my own order this morning with Apple. I’m with Mark Twomey:Upgrading to Snow Leopard is a safe day-1 activity. Most of the updates amount to new under-the-hood features and the OS has been through round after round of testing. Unlike the massive shift from Tiger to Leopard (which I missed, being a late switcher), Snow Leopard ought to be a lesser upgrade.

Why make the update at all? Here are a few of my reasons:

1. It’s cheap: Just $29 to update a single Mac, or $49 for up to five. Compared to Microsoft’s (expired) “limited-time-only” (and incredibly complicated) Windows 7 upgrade, Apple sets out a red velvet carpet.
2. It’s easy: There’s just one version of Mac OS X, and any system running OS X 10.5 “Leopard” can update to full-on Snow Leopard. There are no editions and no conflicts updating from 32-bit to 64-bit (like Windows 7).
3. It future-proofs your (Intel) Mac: Mac developers have a long history of quickly leveraging new OS X features since Mac users have a long history of quickly upgrading. Snow Leopard adds cool stuff like Grand Central and OpenCL that my Intel- and Nvidia-based Macs ought to be able to leverage. See below if your Mac can use these, too!

Sure, there aren’t any amazing features like Time Machine to set the world on fire. But the Snow Leopard update is still a slam-dunk for any Intel-based Mac user! My Late-2007 MacBook Pro will get everything but H.264 acceleration and my 2009 Mac Mini is all set to go!

Updated with Mac Mini and Xserve information. Keep the suggestions coming and test that EFI! Picked up, colorized, and reused (with permission) by the excellent Ed Bott in his ZDNet column!

Note: Some of these links include affiliate codes that help pay for this blog. For example, buying an Amazon Kindle with this link sends a few bucks my way! But I don't write this blog to make money, and am happy to link to sites and stores that don't pay anything. I like Amazon and buy tons from them, but you're free to buy whatever and wherever you want.

© sfoskett for Stephen Foskett, Pack Rat, 2009. | Mac OS X 10.6 “Snow Leopard”: In Our Hands August 28!
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This last point has always been debatable as well. Apple tends to select higher-end x86 parts for their Macs and has led the way with innovative chassis, screen, and trackpad technology. But PC makers have quickly followed, offering part-for-part Apple clones at 80% of the cost. This week, however, I stumbled onto a concrete difference between Mac and PC hardware that has real-world impact: Across the board, Apple uses exclusive Intel CPUs with enhanced capabilities to support virtualization of 64-bit operating systems, including Windows 7′s special XP compatibility mode.

Virtualization-Ready

Virtualization hypervisors have become very widespread and popular, especially in the Apple world. Mac users regularly list Parallels Desktop and VMware Fusion among their favorite applications, since they open up the wide world of Windows applications running in a virtual machine. Although most daily tasks can be performed with native OS X applications, some apps just aren’t available.

Personally, I use Fusion on OS X with Windows Vista to occasionally run Microsoft’s Visio and Outlook, both of which aren’t available as native applications. I also use a 2009 Mac Mini as a server and virtual computer lab, mainly relying on Sun’s lightweight and free VirtualBox hypervisor. Although it isn’t impressive as the physical lab Dennis Martin described to me last week, I am able to run a variety of servers (Linux, Windows, and OS X) and other virtual gear (Windows Storage Server and FreeNAS) to simulate enterprise IT environments.

Windows users have less need to run virtualization applications: When your operating system commands over 90% of the market, a whole world of applications is at your fingertips! But enthusiasts and corporate IT types love virtualization, and VMware Server and Microsoft Hyper-V are commonly found on their Windows machines.

64-Bit Road Block

These popular virtualization packages support a wide range of modern hardware, but not everything works perfectly. Hypervisors had trouble with many tasks, particularly running 64-bit operating systems, until Intel and AMD introduced special hardware-assisted virtualization capabilities in their CPUs. The latest hypervisors and CPUs can now even virtualize 64-bit operating systems on top of 32-bit hosts!

But not all CPUs include this technology. Intel has a long history of artificially segmenting their product line by disabling certain features in low-end parts. For their Core 2 Duo “Merom” and “Penryn” lines, Intel decided that their VT virtualization technology would be the differentiator. Therefore, a lack of VT support is one of the main differences between low-end and high-end Intel Core 2 Duo CPUs.

Many of the latest portable and compact desktop systems use Intel’s Penryn-3M line, including Apple’s MacBook, MacBook Pro, and Mac Mini systems. See the issue here? Intel’s lower-end 2.0 GHz and 2.133 GHz CPUs (P7350 and P7450, respectively) don’t support VT, which means that systems using them don’t have the latest VT hardware virtualization capability and thus can’t run 64-bit virtual machines!

This is an issue for users of popular Sony Vaio, Dell Inspiron, and HP Pavilion PCs, and is likely to become much more important soon. See, Windows 7 includes a special XP compatibility mode, which is really just a virtual machine running XP under 7. But XP mode will not work without Intel VT or AMD-V. This means that XP mode in Windows 7 won’t work on the very mass-market machines that would benefit most from it!

Apple’s Different

This sounds terrible: The latest machines won’t run increasingly-popular virtualization software. But there is a very good reason that buyers of the latest Apple machines aren’t up in arms. It seems that Apple made a deal with Intel to get a special version of the Penryn-3M Core 2 Duo CPUs that do support Intel VT!

Apple’s latest Mac Mini, MacBook, and MacBook Pro all sport P7350 and P7450 CPUs, just like competing Dell, Sony, and HP machines. But the Apple CPUs have VT and the PCs lack it. The VT support is gone, and cannot be enabled in the PC BIOS.

So even a PC and Mac sporting the exact same CPU part numbers aren’t equal: Every recent Mac will run 64-bit Windows and XP mode in Windows 7 and many PCs won’t. And I can run anything I want on my Mac Mini virtual lab!

Update - Let me be very, very clear on the facts here:

• Most hypervisors now require Intel VT or AMD-V in order to virtualize 64-bit operating systems
• Microsoft requires this technology to use XP mode in Windows 7
• All current Apple Macs (including those that use P7350 and P7450 CPUs) have Intel VT support in their CPUs regardless of what Intel says on the model spec sheets
• Many PCs use high-end Intel and AMD CPUs that support VT or AMD-V, though some have this turned off in the BIOS
• No PC with an Intel P7350 or P7450 CPU has Intel VT support at all. It cannot be enabled in the BIOS because it does not exist.

I am not an Apple fanboy. I am a virtualization fanboy who is glad I bought a Mac Mini instead of a Dell Studio, HP TouchSmart, or Sony Vaio.

© sfoskett for Stephen Foskett, Pack Rat, 2009. | A Concrete Reason Macs Beat PCs: Intel VT
This post was categorized as Apple, Computer History, Terabyte home, Virtual Storage. Each of my categories has its own feed if you'd like to filter out or focus on posts like this.