Since 2001, the breakthrough technologies and rock-solid UNIX foundation of Mac OS X have made it not only the world’s most advanced operating system but also extremely secure, compatible, and easy to use. Snow Leopard continues this innovation by incorporating new technologies that offer immediate improvements while also smartly setting it up for the future.
New in Snow Leopard:
64-bit computing used to be the province of scientists and engineers, but now this generational shift in computing gives all users the tools to apply the power of 64-bit to speed up everything from everyday applications to the most demanding scientific computations. Although Mac OS X is already 64-bit capable in many ways, Snow Leopard takes the next big step by rewriting nearly all system applications in 64-bit code¹ and by enabling the Mac to address massive amounts of memory. Now Mac OS X is faster, more secure, and completely ready for the future.
The 64-bit transition.
The entire computing industry is moving from 32-bit to 64-bit technology, and it’s easy to see why. Today’s Mac computers can hold up to 32GB of physical memory, but the 32-bit applications that run on them can address only 4GB of RAM at a time. 64-bit computing shatters that barrier by enabling applications to address a theoretical 16 billion gigabytes of memory, or 16 exabytes. It can also enable computers to crunch twice the data per clock cycle, which can dramatically speed up numeric calculations and other tasks. Earlier versions of Mac OS X have offered a range of 64-bit capabilities. Now Snow Leopard takes the next step in the transition from 32-bit to 64-bit.
Built-in applications are now 64-bit.
Nearly all system applications — including the Finder, Mail, Safari, iCal, and iChat — are now built with 64-bit code. So not only are they able to take full advantage of all the memory in your Mac, but the move to 64-bit applications also boosts overall performance. Together with other refinements and improvements in Snow Leopard, this means that just about everything you do — from launching applications like QuickTime to running JavaScript in Safari to opening image files — will feel faster and more responsive.
Ready for the future.
The 64-bit support in Snow Leopard makes Mac OS X completely ready for whatever computing enhancements might arrive in the future. For example, Snow Leopard is ready to support up to 16 terabytes of RAM — about 500 times more than today’s Mac computers can accommodate. That may sound like more RAM than you’ll ever need, but who can predict the requirements of high-performance computers in the future? Mac OS X Snow Leopard comes prepared for anything.
More secure than ever.
Another benefit of the 64-bit applications in Snow Leopard is that they’re even more secure from hackers and malware than the 32-bit versions. That's because 64-bit applications can use more advanced security techniques to fend off malicious code. 
First, 64-bit applications can keep their data out of harm's way thanks to a more secure function argument-passing mechanism and the use of hardware-based execute disable for heap memory. In addition, memory on the system heap is marked using strengthened checksums, helping to prevent attacks that rely on corrupting memory.
64-bit applications in Snow Leopard deliver faster performance at common operations.²
32-bit compatible.
To ensure simplicity and flexibility, Mac OS X still comes in one version that runs both 64-bit and 32-bit applications. So you don’t need to update everything on your system just to run a single 64-bit program. And new 64-bit applications work just fine with your existing storage devices, PCI cards, and Snow Leopard-compatible printers.
More cores, not faster clock speeds, drive performance increases in today’s processors. Grand Central Dispatch takes full advantage by making all of Mac OS X multicore aware and optimizing it for allocating tasks across multiple cores and processors. Grand Central Dispatch also makes it much easier for developers to create programs that squeeze every last drop of power from multicore systems.
With CPUs, more cores is better.
In the past, the best way for computer chip makers to improve performance was to turn up the clock speed on the processor. But that generates more heat and consumes more power, which is bad for computers, especially notebooks. So instead the industry has moved to chips with multiple processor cores, which can provide more performance while consuming less power. Today every Mac runs on one or more multicore Intel processors.
Multicore. Multiple challenges.
To take full advantage of these processors, software applications must be programmed using a technology called threads. Software developers use threads to allow multicore processors to work on different parts of a program at the same time. However, each application must do its own threading, which reduces the efficiency of the entire system. And because threads can be difficult to program, many developers don’t invest the effort to make their applications multicore capable. Consequently, lots of applications aren’t as fast as they could be.
Introducing Grand Central Dispatch.
Grand Central Dispatch (GCD) in Mac OS X Snow Leopard addresses this pressing need. It’s a set of first-of-their-kind technologies that makes it much easier for developers to squeeze every last drop of power from multicore systems. With GCD, threads are handled by the operating system, not by individual applications. GCD-enabled programs can automatically distribute their work across all available cores, resulting in the best possible performance whether they’re running on a dual-core Mac mini, an 8-core Mac Pro, or anything in between. Once developers start using GCD for their applications, you’ll start noticing significant improvements in performance.
A finely tuned engine.
Grand Central Dispatch is extremely efficient at what it does. It dynamically scales the workload of an application to account for the number of processors in the computer. And it makes applications more efficient by using only the number of threads required for the work being done. For example, without GCD, if an application needs 20 threads when at maximum capacity, it might set up 20 threads and consume the associated resources even when it has nothing to do. GCD, by contrast, frees resources when it’s not using them, helping to keep the whole system more responsive. Imagine the efficiency and performance gains if every application on your Mac were using GCD.
Built into the core.
Grand Central Dispatch is deeply integrated into Mac OS X Snow Leopard, making it easier for all kinds of applications to take better advantage of multicore processors. In addition, your Mac as a whole becomes more efficient at handling numerous tasks at the same time, resulting in performance gains across the board.
Powerful developer tools.
Developers will program for Grand Central Dispatch using the Xcode tools included with every Mac. They can use the Xcode debugger and Instruments performance analysis tool to get insights into GCD at runtime. These tools make it possible to quickly inspect any GCD work queue, even down to a specific block of executing code, giving developers a complete understanding of their application as GCD efficiently assigns tasks to each available core.
Learn more about developing for GCD
Read the GCD technology brief
With graphics processors surpassing speeds of a trillion operations per second, they’re capable of considerably more than just drawing pictures. OpenCL in Snow Leopard is a technology that makes it possible for developers to tap the vast gigaflops of computing power currently in the graphics processor and use it for any application.
The skyrocketing power of GPUs.
Over the last few years the performance of graphics processing units (GPUs) 
has grown exponentially as measured in gigaflops. Today’s fastest GPUs are capable of over one teraflop, as much as the room-size ASCI RED supercomputer of just 12 years ago.
A graphic shift in performance.
Now a new technology in Mac OS X Snow Leopard called OpenCL takes the power of graphics processors and makes it available for general-purpose computing. No longer will graphics processors be limited to graphics-intensive applications such as games and 3D modeling. Instead, once developers begin to use OpenCL in their applications, you’ll experience greatly improved speed in a wide spectrum of applications.
For example, sophisticated financial modeling techniques can be incorporated into desktop accounting software and personal finance software. Media applications can perform complex, intensive operations with larger video and graphics files. Games can have more realistic physics simulations. And scientists and researchers can tackle far more challenging problems using their everyday Mac computers.
Optimized for
the task.
OpenCL automatically optimizes for the kind of graphics processor in the Mac, adjusting itself to the available processing power. OpenCL provides consistent numeric precision and accuracy, fixing a problem that has hampered GPU-based programming in the past.
Familiar, C-based language with industry support.
OpenCL stands for Open Computing Language. It’s a C-based programming language with a structure that will be familiar to programmers, who can simply use Xcode developer tools to adapt their programs to work with OpenCL. They don’t have to completely rewrite applications to use OpenCL. They need only rewrite the most performance-intensive parts of their application in OpenCL C. The vast majority of application code can be left unchanged. Best of all, OpenCL is an open standard that’s supported by the biggest names in the industry, including AMD, Intel, and NVIDIA.
Read the OpenCL technology brief
Snow Leopard introduces QuickTime X, a major leap forward that advances modern media and Internet standards. QuickTime X includes a brand-new player application, offers optimized support for modern codecs, and delivers more efficient media playback, making it ideal for any application that needs to play media content.
Another leap forward.
QuickTime X is the next-generation media technology that powers the audio and video experience in Mac OS X Snow Leopard. From 
its inception in 1991, QuickTime has stood at the forefront of video technologies — first with software-based video, then with Internet video. Now QuickTime X takes another leap forward by building on the amazing media technologies in Mac OS X — such as Core Audio, Core Video, and Core Animation — to deliver enhanced playback, greater efficiency, and higher quality.
A new QuickTime Player.
QuickTime X debuts a brand-new version of QuickTime Player, the standalone application used by millions to watch QuickTime-based video. Using the power of the Core Animation technology in Mac OS X, QuickTime Player offers a clean, uncluttered interface with controls that fade out when they’re not needed. And large thumbnail images make navigating chaptered movies simpler than before.
With a single click, QuickTime Player can now capture audio or video using the built-in camera and microphone in your Mac. You can easily trim media to the perfect length, then send it to iTunes for syncing to an iPhone, iPod, and Apple TV. You can also use QuickTime Player to publish your media to MobileMe or YouTube — without worrying about codec formats or resolutions.
Built for smooth playback.
QuickTime X is optimized for the latest modern media formats — such as H.264 and AAC — through a new media architecture that delivers stutter-free playback of high-definition content on nearly all Snow Leopard-based Mac systems. QuickTime X maximizes the efficiency of modern media playback by using the graphics processor to scale and display video. QuickTime X further increases efficiency by supporting GPU-accelerated video decoding of H.264 files.
Video streaming from any server.
QuickTime X takes Internet video streaming to new levels with support for HTTP live streaming. Unlike other streaming technologies, HTTP live streaming uses the HTTP protocol — the same network technology that powers the web. That means QuickTime X streams audio and video from almost any web server instead of special streaming servers, and it works reliably with common firewall and wireless router settings. HTTP live streaming is designed for mobility and can dynamically adjust movie playback quality to match the available speed of wired or wireless networks, perfect whether the video is watched on a computer or on a mobile device like iPhone or iPod touch.
High performance, high quality.
Because it’s built into the heart of Snow Leopard, QuickTime X uses Mac OS X technologies such as Cocoa, Grand Central Dispatch, and 64-bit computing to deliver greatest-possible performance and enables QuickTime Player to launch up to 2.4x faster.2 QuickTime X also takes advantage of ColorSync to provide high-quality color reproduction during playback and when sharing media to your iPhone, iPod, or Apple TV.
