64-Bit Computing Has Finally Arrived

by John Brandon

In technology, some ideas take time to germinate, none more so than 64-bit computing, where the operating system and software (including most drivers) run on a 64-bit CPU from Intel or AMD. Linux has been 64-bit for eight years, and Apple's operating system for five. But compatibility problems have dogged the 64-bit versions of Windows since its introduction in Windows XP. There are several key advantages, such as improved performance and support for many gigabytes of RAM. The real question is, why 64-bit—and why now? And, why should you care?

Let's be honest: The promise of 64-bit computing has been around for a while—some would say it's a broken promise. Yet the planets have finally aligned: Microsoft offers a 64-bit version of both Windows Vista Ultimate and Windows XP Pro, and 64-bit versions of Linux are freely available. According to Gartner, one out of every four PCs sold today comes with a 64-bit OS installed. As for hardware, both Intel and AMD have offered 64-bit processors for years. And the additional RAM supported by the wider data bus is now amazingly affordable, thanks to a streamlined manufacturing process and mainstream levels of demand.

Most important, companies such as Adobe, Apple, and Autodesk (and that's just those that start with the letter A) now offer their flagship software products in 64-bit versions. Adobe, for the first time, offers its Creative Suite 4 in a 64-bit version—currently for PC only, with a Mac version in the works.

The main benefit has to do with memory addressing. A quick lesson in processor technology: Long ago, the brilliant minds in computer science (engineers working at Intel and other companies) decided that a PC would need only a 32-bit "register size"—the amount of RAM a CPU can access. In mathematical terms, that's 232 or exactly 4GB of RAM. Back then, the high cost of memory and the absence of 64-bit software or operating systems meant that few imagined a CPU running in 64-bit mode.

Fast-forward to 2003. AMD released the first 64-bit processor, the Opteron. Suddenly, the rules changed. The CPU could access an astonishing amount of RAM: exactly 264, which translates to several million gigabytes of RAM. Not that you would install that much memory—but you could if you wanted to. Since then, operating systems and software have been slowly catching up to the hardware, and today they have (finally!).