When Apple introduced the Power Mac G5 in 2003, it was touted as “The world’s first 64-bit personal computer.” This was due to its IBM PowerPC G5 processor’s 64-bit architecture, which enabled the Power Mac G5 to break through the 4GB barrier and support up to 8GB of RAM. 64-bit hardware has been around since 2003, and Mac OS X has been consistently updated to support more and more levels of 64-bit operation.
While 10.4 only supported 64-bit command-line tools and 10.5 added support for 64-bit GUI applications, 10.6 introduced a 64-bit kernel along with 64-bit built-in applications (such as Finder, Mail, Safari, and iCal). Back in 2003, Apple’s hardware was more capable than its software could operate.
With 64-bit technology, today’s Snow Leopard operating system software can support up to 16TB of RAM, 200 times the 64GB that can be installed in the highest end current Mac Pro. You may be asking, “Why would anyone ever need 16TB of RAM?” One of the benefits of 64-bit is the ability for an individual application to access more than the 2GB memory limit that 32-bit operating systems impose (2GB for the kernel, 2GB for applications).
What this means is that more and more of an application’s data can be stored in super-fast RAM. These are performance gains that any user can appreciate. Lion, Apple’s next operating system, is said to adopt 64-bit to the extent that some Intel machines from 2006 using the Core Solo or Core Duo (as opposed to Core 2 Duo) will not be supported because of their 32-bit architecture.
While some 5 year old machines might not be able to run software yet to be released, the lack of support is a small price to pay for the overall performance increases that Apple’s 64-bit implementation will bring.