Microsoft Windows XP Professional x64 Edition (XP64) uses the full power of modern 64-bit processors (the first pillar) and makes that power available to compatible 64-bit programs. Or it would if there were any. So we have a Colosseum and a playing field, just no gladiators.
Still, for forward-looking early adopters, we put XP64 through its paces to see what you can expect.
The good news: Most 32-bit applications work fine under XP64 and may get a small performance boost. The bad news: Some programs, particularly low-level system utilities and drivers, just arent compatible.
Before we delve into the details, though, lets give a little background. A 32-bit processor cant address more than 4 gigabytes (232 bytes) of memory. The memory space of a 64-bit processor can theoretically span 16 terabytes. Thats a lot—the text of all the books in the Library of Congress would occupy about 20TB.
A 64-bit program can allocate all available physical and virtual memory, as opposed to the 2GB-per-process limit for 32-bit programs. And 64-bit programs get an additional boost by taking advantage of the processors 64-bit internal registers.