Snow Leopard features several new under-the-hood technologies that, at first glance, might seem to be of interest only to Mac software developers. But those technologies will in fact benefit regular Mac users--if not right now, then in the not-too-distant future. Here's a look at how three of these additions to Snow Leopard -- 64-bit computing, Grand Central Dispatch, and OpenCL -- work and how they could improve your Mac experience sometime soon.
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From 32 to 64 bits
Three years ago, Apple trumpeted the fact that Leopard would support 64-bit processing. Back then, the announcement seemed more academic than exciting, since only high-end Macs had 64-bit processors. But these days, every Mac model is powered by a 64-bit CPU (from Intel's Core 2 Duo and Xeon lines). That's why 64-bit support in Snow Leopard is relevant to all of us: Apple has updated just about every program and subsystem that's a part of Snow Leopard to run in 64-bit mode.
There are two reasons this is a good thing. The first is simple: You need a 64-bit OS if you want programs on your computer to have access to more than 4GB of RAM. Snow Leopard can address a staggering 16 terabytes of RAM. It'll be a while before computers with that much hard-drive storage -- let alone RAM -- are in wide use. But moving to 64-bit computing does give future Macs plenty of breathing room.
While there are distinct 32- and 64-bit versions of programs and operating systems on the Windows side, on the Mac there's just one version of everything. Snow Leopard will run on a 32-bit system (like, say, an Intel Core Duo iMac) just fine. But that's only because each of Snow Leopard's applications actually contains two versions of the program, nestled inside its application package--a 32-bit program file and a 64-bit version. (It's the same system that Apple used to let developers embed PowerPC and Intel versions of their apps in single application packages.) When you double-click on the app, Snow Leopard senses whether you're in 64-bit or 32-bit mode and launches the proper version. (If for some reason you'd prefer to run the 32-bit version on a 64-bit system, you can do that too: select the app in the finder, choose Get Info, and click the "Open in 32-bit mode" check box.)