Although positioned as an under-the-hood upgrade to Leopard, Apple Mac OS X 10.6 Snow Leopard offers a lot of changes on the surfaces as well.
Mac OS X 10.6 Snow Leopard: Speed and stability
Most of the time, software upgrades add new features at the expense of speed. But since Snow Leopard was announced, Apple has repeatedly said that this update is about not just fixing bugs and making tweaks, but improving performance.
When it comes to speed, there are actually two Snow Leopard stories. One is about the speed boosts the system provides today. The other is about the potential speed boosts that users may see in the future, as both software and hardware continue to evolve.
Let's start with the present. Macworld Lab compared Leopard to Snow Leopard in 16 different speed tests on three different systems. On half of our tests, Snow Leopard showed definite speed improvements when compared to Leopard.
In two other tests, Leopard was slightly faster than Snow Leopard; in the rest, the results were either a mixed bag or identical between operating systems.
My subjective experience using Snow Leopard for several weeks is essentially consistent with those lab results. Some tasks simply feel faster in Snow Leopard than in Leopard, while others seem no different at all. In general, I think most users will find that Snow Leopard feels faster and runs smoother than its predecessor.
Snow Leopard 64-bit computing
The use of 64-bit computing will greatly improve the capabilities of computers. For example, 32-bit software can access only 4 GB of RAM at a time; 64-bit computing expands that ceiling to 16 exabytes. That's 16 billion gigabytes.
Plus, 64-bit applications run faster on computers with Intel Core 2 Duo or Xeon processors. They can crunch 64-bit code twice as fast per clock cycle as computers running in 32-bit.
Apple touts Snow Leopard as being first Mac OS to finally support 64-bit from top to bottom, although the default kernel status for all consumer Macs is the 32-bit kernel. Snow Leopard supports 64-bit applications even while running 32-bit drivers. Basically, whether the machine is booted into the 32-bit kernel or the 64-bit kernel, any application that can run at 64-bit will run in that mode automatically.
By having Snow Leopard boot into the 32-bit kernel, Apple improves software compatibility. That's because kernel extensions must match the kernel's mode, or they don't work. While Apple did a fine job porting over its native applications for 64-bit compatibility, there are still some third-party vendors that haven't released updates for their software (such as the aforementioned Cisco VPN software) yet.
Snow Leopard: new technologies
In the future, however, the software than runs on Snow Leopard has the potential to become dramatically faster. That's because Apple has provided two technologies for software developers that should enable them to give their apps a speed boost, provided they put in the work to take advantage of the new technologies.
One technology new to Snow Leopard is the OpenCL standard, which promises to speed things up without any changes to your hardware needed.
While CPU manufacturers have shifted from increasing processor clock speeds to adding more cores to processors, graphics chip makers have continued pushing the boundaries to boost the processing power behind their graphics cards.
Years ago, Apple began offloading animation effects from the CPU to the graphics processing unit (GPU), freeing up the main processors for actual data-crunching.
Every version of Mac OS X in recent years has increasingly utilized the GPU for computationally expensive tasks. In 2006, Apple unveiled Core Image and Core Animation with Mac OS X 10.4, technologies that allow real-time image and video effects to be handled by the graphics cards.
With Snow Leopard, Apple takes GPU acceleration to another level by developing and publishing an open standard to offload even more work to GPUs.
Enter OpenCL, a language and runtime framework that allows developers to crunch any data-parallel algorithms on any free processing core, automatically, without needing to code for specific circumstances.
The best part for Mac owners is that OpenCL works with all GPUs and CPUs available in Apple's current line-up. The best part for developers is that only the most performance-intensive aspects of their software need be rewritten to take advantage of the new technology.
While OpenCL bridges the gap between software and the available processing cores on a computer, the new problem is how to account for all these cores and software instruction threads.
That's where Grand Central Dispatch (GCD) comes in. Grand Central Dispatch is the foundation for keeping everything running smoothly; it acts like a built-in air traffic control centre, dynamically adjusting computer workload based on available hardware and resources.
If the resources are available, GCD speeds things up. If the computer is busy, GCD backs off. In concert with OpenCL and 64-bit, Grand Central Dispatch should lead to a big jump in performance and optimization as applications are updated.
In truth, neither of these features is a reason to buy Snow Leopard today. But they will help make the next Mac you buy be much faster than it would have been otherwise.
Snow Leopard stability
Generally every major operating-system upgrade steps forward in terms of features and backward in terms of stability. Apple's engineers have had nearly two years to wring the bugs out of Leopard; the new features introduced in Snow Leopard will have no doubt introduced some new ones.
But I'm happy to report that, in general, Snow Leopard seems as stable as it seems fast. Yes, I did see a few crashes from Safari, and I also experienced more crashes in Mail than I had experienced when using Leopard. Presumably Apple will address these sorts of bugs with forthcoming updates to Snow Leopard, but stability issues have never made me feel regret about switching from Leopard to Snow Leopard.
NEXT: Snow Leopard: Application tweaks >>