a variant of compactflash known as cfast is based on the serial ata bus, rather than the parallel ata/ide bus for which all previous versions of compactflash are designed. cfast is also known as compactfast. cfast supports a higher maximum transfer rate than current compactflash cards. as of 2011, sata supports transfer rates up to 600 mbyte/s while pata is limited to 167 mbyte/s using udma 7. cfast cards are not physically or electrically compatible with compactflash cards. however, since sata can emulate the pata command protocol, existing compactflash software drivers can be used, although writing new drivers to use ahci instead of pata emulation will almost always result in significant performance gains. cfast cards use a female 7-pin sata data connector, and a female 17-pin power connector, so an adaptor is required to connect cfast cards in place of standard sata hard drives which use male connectors.