ReadyBoost is a new feature of Windows Vista which uses flash memory on a USB drive to boost system performance.  It uses the USB drive as a hard disk cache and/or virtual memory store to speed up file access and increase the apparent RAM available. 

Many people have asked on forums how this could possibly be effective – after all, flash memory has a much slower data transfer rate than most hard disks.  That’s true, but the trick is that good flash memory has a much lower seek time than a hard disk.  By placing many small files on the USB drive, Windows can randomly access these files much more quickly than is normally possible from a hard disk.

The key point is that the USB drive must have very fast seek times.  Many USB flash memory devices, even those with high data transfer rates, don’t have sufficiently fast seek times to make them useful for ReadyBoost.  Unfortunately, manufacturers don’t normally publish random seek times for flash memory like they do for hard disks.  This makes shopping for a ReadyBoost compatible flash drive a bit of a lottery.

It’s possible to force Windows to accept any device for ReadyBoost use via a registry hack.  However, this is not recommended, as the high latency will reduce system performance rather than improve it.

I searched everywhere for a definitive source of ReadyBoost compatible devices, but I couldn’t find one.  So I decided to start one of my own.  You can access it here: ReadyBoost Compatibilty Chart

If you’re currently using Vista and have tried ReadyBoost with your device, please submit your results here.

Comments are welcome!