Despite the fact that Microsoft has expressed its official position regarding testing Windows Vista Service Pack 1 ahead of its finalization, there is simply too much of a hunger for the service pack. In this context, performing benchmark tests on development milestones of Vista's first refresh are inherent methods of getting a taste of what SP1 will bring to the table. The Redmond company revealed in the past that it considers irrelevant tests involving a pre-RTM build of Vista SP1. But with the release to manufacturing date of the service pack still to be announced, sometime in the first quarter of 2008, the temptation is too big to get a sneak preview of the refresh.

In an initiative similar to that of the Devil Mountain Sofware company that tested the performance of beta builds of XP SP3 and Vista SP1, Gizmodo has also performed a benchmarking of Vista SP1, but this time the full Release Candidate. Earlier in December, Microsoft opened up the beta testing process of Vista SP1, with the delivery of the first public download, namely Release Candidate 1. Now, there is still no word from Microsoft whether RC1 is the final stage before RTM or if another RC will follow, but the company has given strong indication that Vista SP1 RC1 is close to the service pack's final form.

The new performance tests are essentially a comparison between Vista SP1 RC1, Vista RTM and Windows XP SP3. The tests were performed on a machine with the following configuration: a dual quad-core Penryn HP xw8600 PC, NVidia Quadro FX 4600 graphics (eight processor cores each at 3.16GHz), a 15,000rpm SAS hard drive and 4GB of physical system memory. Vista SP1 RC1 scored the highest, according to the results returned by running the industry-standard PCMark05 benchmark, accounting for 15.28% speed increase, compared to the RTM version of Vista. However, when it came down to network transfers, Vista SP1 RC1 hit a speed bump and copied a 1.37GB folder with 2606 items in almost 16 minutes, whereas Vista RRm did it in 13 minutes and XP SP2 in under 4 minutes.