Abbreviated as HHDD, a hybrid hard disk drive is a large-buffer computer hard drive that uses non-volatile flash memory (also known as NVRAM) to cache data during normal use. Hybrid hard drives uses 128MB (or more) of high speed flash memory, which is embedded directly on the hard drive itself, to serve as a fast cache for booting and saving data. When booting the PC, the operating system loads data from the flash memory first, speeding boot-up times and it also removes the need to quickly spin up the drive, which saves on power consumption as well. HHDs released by both Samsung and Seagate in 2007 are also called ReadyDrive (the name used by Microsoft) and it is a Windows Vista only technology. The first hybrid hard disk drives were 2.5-inch drives for notebooks.