The 64-bit edition of Windows Vista delivers not only support for larger quantities of system memory, with the high-end editions supporting as much as 128 GB of RAM, but also some extra horse power hidden under the hood. Essentially, in terms of performance, x64 Vista manages to best all the alternatives available under the Windows client umbrella. However, it's not the x64 Vista with Service Pack 1, as you would expect, but the plain vanilla RTM version of the latest Windows client we're talking about. In a benchmark performed using PassMark PerformanceTest 6.1, the RTM version of 64-bit Vista came out on top of all 32-bit and 64-bit Windows clients starting with the original version of Windows XP.

According to Hardware 2.0, x64 Vista RTM has outrun x64 Vista SP1 with a score of 1183.1 compared to just 1128.8. The platform used for testing featured a Phenom 9700 quad-core processor, an ATi Radeon 3850 256MB RAM, an ASUS M3A32-MVP Deluxe, 2GB (2 x 1GB) RAM, and a Western Digital Raptor HDD 10,000RPM 150GB as well as a Western Digital Caviar HDD 7,200RPM 500GB. On this system, the original 64-bit Vista version bested the SP1 release.

In this context, both 64-bit variants of Vista (with and without SP1) outperformed the 32-bit versions, also RTM and SP1. x86 Vista RTM even scored higher than x86 Vista SP1 with a rating of 1002.4 compared with just 972.3 of the operating system plus the service pack. But, at the same time, both XP RTM and XP SP3 scored higher than 32-bit Vista SP1. XP RTM pulled off a score of 1001.4, while XP SP3 with 990.8 bested not only x86 Vista SP1 but also XP SP2 with just 891, the lowest score of the benchmark. Still, the obvious conclusion of the tests is that while 64-bit Vista editions run faster than any other Windows client, the differences between the 32-bit variants of the operating systems are only superficial, and won't be felt in a real life scenario.