Mac OS X v10.6 "Snow Leopard"

Main article: Mac OS X Snow Leopard
Mac OS X v10.6 "Snow Leopard" was released on August 28, 2009. Rather than delivering big changes to the appearance and end user functionality like the previous releases of Mac OS X, Snow Leopard focuses on under the hood changes, supposedly increasing the speed, efficiency, and stability of the operating system. For most users, the most noticeable changes are: the disk space that the operating system frees up after a clean install compared to Mac OS X 10.5 Leopard, a more responsive Finder rewritten in Cocoa, faster Time Machine backups, more reliable and user friendly disk ejects, a more powerful version of the Preview application, as well as a faster Safari web browser.

The rewrite of Finder in Apple's native Cocoa API allow the Finder to take advantage of the integrated 64-bit technology as well as Grand Central Dispatch, use a more user-friendly disk eject (clearer dialogs will notify the user of what services or programs are using a given disk), and provides it a more responsive feel overall.
The new Safari 4 includes a boost in JavaScript and HTML performance, which results in faster web browsing. The majority of this performance boost is enabled by the new SquirrelFish JavaScript interpreter, improving the JavaScript rendering speed of Safari by over 50%.[82] The new Top Sites also displays the most frequently visited and/or bookmarked sites in a panorama view, allowing the user to easily access their favorite sites along with a new Cover Flow view for the user's browsing history. Safari 4 is now also more crash resistant, being able to isolate plug-ins which are the number one cause of web browser crashes.[83]
Mac OS X v10.6 also features Microsoft Exchange Server support for Mail, iCal, and Address Book, new 64-bit technology capable of supporting greater amounts of RAM, an all new QuickTime X with a refreshed user interface and more functionality that used to be only available to Quicktime Pro owners.
Back-end platform changes include improved support for multi-core processors through Grand Central Dispatch which attempts to ease the development of applications with multi-core support, and thus improve their CPU utilization. It used to be that developers needed to code their programs in such a way that their software would explicitly take advantage of the multiple cores, which could easily become a tedious and troublesome task, especially in complex software. It also includes advanced GPU performance with OpenCL (a cross platform open standard for GPGPU distinct from CUDA, Dx11 Compute Shader or STREAM) by providing support to offload work normally only destined for a CPU to the graphic card's GPU. This can be especially useful in tasks that can be heavily parallelized.
Snow Leopard supports only machines with Intel CPUs, and drops default support for applications built only for the PowerPC architecture (Rosetta can be installed as an additional component to retain support for PowerPC-only applications).
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