ReadyBoost (codenamed EMD) is a disk caching software component developed by Microsoft for Windows Vista and included in later versions of the Windows operating system. ReadyBoost enables NAND memory mass storage devices, including CompactFlash, SD cards, and USB flash drives, to be used as a write cache between a hard drive and random access memory in an effort to increase computing performance. ReadyBoost relies on the SuperFetch technology and, like SuperFetch, adjusts its cache based on user activity. Other features, including ReadyDrive, are implemented in a manner similar to ReadyBoost.