ReadyBoost is a memory extension for Windows Vista. It works very much like the swap file on the hard drive, but it is not used as an active extension to the main memory. Instead, Windows uses it to pre-cache application data for popular programs.

ReadyBoost is meant to support the new SuperFetch feature by adding more memory to the system. Microsoft's intended storage device is a USB 2.0 Flash memory stick, mainly because these products are incredibly affordable and reasonably fast. Knowing that USB 2.0 memory sticks deliver between 5 MB/s and 30 MB/s you might wonder how this makes sense.

Most USB 2.0 Flash memory devices on the market offer a capacity of 512 MB to 4 GB. There are smaller and even larger products available; the mainstream is at around 1 GB. These storage devices are very popular, as they are durable and small, and they can be used as a key fob. Many users use USB Flash memory sticks today as they used to jockey floppy disks.

The strength of Flash memory isn't exception transfer performance, but access times that can almost be called nonexistent. Even if you got a memory stick that doesn't provide more than 15 MB/s, it will still benefit from its DRAM-like access times. Compared to a hard drive, which might not be able to provide requested data at its maximum transfer performance of 60-80 MB/s due to higher priority system requests, the USB 2.0 Flash device should be available for serving the SuperFetch purpose. Even the separation of swapped data on the hard drive, and superfetched application data on a USB Flash device provides a small advantage.

When you check out our test results later on you will realize that the memory expansion by means of an USB 2.0 Flash memory device does indeed have a positive impact on application launch time. If you already have a high-speed USB 2.0 Flash memory device at 512 MB or higher capacity you should consider plugging it into an available USB 2.0 port. Windows will prompt you as you plug it in, but instead of opening an Explorer window to access the device's content you can now assign it for use with ReadyBoost. You can use the whole capacity or reserve a smaller capacity for ReadyBoost. It's important to know that Windows doesn't store critical data onto the USB device, which means that you can remove it at any time without facing any kind of data loss. The only impact might be longer application launch times.