Leopard now features full 64-bit computing through out its whole OS architecture. So what does this mean? In simple terms, your apps will be able to access more memory and if supported by the application, can do approx twice the work of a a standard 32-bit application. Most people however will not see 64-bit as a huge advantage at all. If you're into dealing with very large photos or movie files, this is where you'll see some significant gains in performance. Why is this? Again, 64-bit processing will allow allocation to more memory to any app that can take advantage of it. Also, it will allow the processor to do more work per clock cycle (think 1's and 0's). When Apple was building in 64-bit into OS X, they did it in a way that allows 32-bit backwards compatibility. What does this mean? This means that you won't have to have to look specifically for 64-bit applications, printer drivers, camera drivers, etc. If it needs to use a 32-bit driver, it will automatically use it on the fly. So everything is backwards compatible. If it can utilize 64-bit processing then it will use it, if not, then it will use 32-bit processing. As the OS and other 3rd party applications get more and more complex, it will become more and more important to getting things done more efficiently. Explaining 64-bit processing in simple terms is very hard to do. Hopefully this gives you an idea of how it works.

Macintosh Computers that support 64-bit
computing:
PowerMac G5 (All
models)
Intel iMac G5 and Intel Core 2 Duo (excludes G3/G4 models)
MacMini w/Intel Core 2 Duo (excludes G4/Intel Core Duo and Solo
models)
MacBook w/Intel Core 2 Duo (excludes Intel Core Duo
models)
MacBook Pro w/Intel Core 2 Duo (excludes Intel Core Duo
models)
Mac Pro (All
models)
Xserve w/Intel Xeon Duo (excludes G4/G5 models)
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