Benchmarked: Windows 7 RTM versus Vista and XP

With Vista, Microsoft introduced a new technology called SuperFetch for caching applications and speeding up boot times. This feature preloads frequently-used applications into memory, so they can be accessed quicker when they're needed.

For conventional magnetic hard drives, this technology makes sense. But if an SSD is used for mass storage, it's better to turn SuperFetch off. The superior access times of SSDs mean they launch applications much faster than magnetic drives, so SuperFetch makes little difference.

Microsoft indicated in a blog entry in May that Windows 7 would disable SuperFetch on systems using SSDs. The company also said that other features such as Defrag and ReadyBoost would not be used under Windows 7. However, in the RTM version (7600.16385), only Defrag is in fact inactive for SSDs -- SuperFetch and ReadyBoost start just as they would with a magnetic disk.

The SuperFetch feature in Windows 7 differs significantly in approach and cache usage from its counterpart in Vista. Under Vista, the caching of applications starts immediately at launch. As the graph below shows, after three minutes just over 1GB of memory has been allocated. In Windows 7, SuperFetch starts after five minutes and after 10 minutes a little more than 600MB has been allocated. By that point, Vista's SuperFetch has allocated more than 1.5GB.

Even without SuperFetch turned on, Windows 7 makes fewer demands on cache. For operating system-related functions, it uses 333MB, while Vista without SuperFetch uses 519MB of cache.

The new implementation of SuperFetch under Windows 7 has a positive impact on performance. Windows 7 clearly makes do with fewer resources, so its cache usage is significantly lower than Vista's. SuperFetch also starts much later, so the hard drive is not tied up immediately after the launch of the operating system. That means you don't have to wait while the operating system monopolises system resources for its caching tasks.