Readyboost is add-on memory for your Windows Vista operating system. With Readyboost one may use flash memory devices such as USB flash drives to improve PC performance. USB Readyboost allows increased PC performance without having to install additional memory on the motherboard, but rather externally via USB port.
The newly inserted memory serves as additional cache location for RAM - or memory which the computer can access faster then a system hard drive. The Windows Vista OS will allow the user to secure the flash memory space so that other tasks cannot use that memory, for example, once a flash drive has been assigned as the Readyboost flash drive you can no longer use that device to save files or play music or retrieve videos and pictures.
However, the Readyboost utility does give the user an ability to designate only portions of the memory for improving PC performance. Need a Readyboost flash drive?
Source: Microsoft
