What's the real deal with 64-bit computing in Snow Leopard?

Is Snow Leopard a 64-bit operating system? Well, yes and no.

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It also means that Apple has made all the pieces of the OS that application developers need to tap into (mainly frameworks) ready and able to accept any 64-bit applications. In other words, Apple is paving the way for developers to create new Mac software that performs better, faster and more reliably.

64-bit and 32-bit side by side

One of the biggest accomplishments of Snow Leopard is that 64-bit and 32-bit applications can run side by side with no disruption to or input from the user. Launch a 32-bit app and it works; launch a 64-bit app next to it and it works. Users don't need to be concerned with whether an application is 32-bit or 64-bit -- they'll just notice that 64-bit apps run faster and may be a little bit more stable.

Note that not all Intel-based Macs (which are the only Macs capable of running Snow Leopard) are 64-bit machines. The first Intel Macs, released in early to mid-2006, were built around Intel's 32-bit Core Duo and Core Solo processors rather than the 64-bit Core 2 Duo and Xeon processors. While only a handful of models (the first Intel iMacs, MacBook Pros, MacBooks and Mac minis) contain the 32-bit processors, it meant that Snow Leopard and the apps that run on it had to be designed to run in either 32-bit or 64-bit operation.

Apple has done this in its own applications and other system components, and the developer tools it provides for Snow Leopard make it easy for third-party developers to create products that can run on either 64-bit or 32-bit Macs. If a user's Mac is a 32-bit machine, it will simply run Snow Leopard and all applications in 32-bit mode.

It's also worth noting that Snow Leopard's predecessor, Leopard, was capable of running 64-bit applications when it shipped two years ago. However, at that time, many of the core applications of Mac OS X weren't written to take advantage of 64-bit operation, and neither were most third-party apps.

Today we're at a midway point between 32-bit and 64-bit computing. What Apple has done in Snow Leopard is to ensure that almost any part of the operating system can run in either 32-bit or 64-bit operation -- and that by default, the vast majority of components run in 64-bit mode.

Ryan Faas is a frequent Computerworld contributor specializing in Mac and multiplatform network issues. His newest book, iPhone for Work: Increasing Productivity for Busy Professionals, will be available from Apress this fall.

Copyright © 2009 IDG Communications, Inc.

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