<P> Hard disk drives are accessed over one of a number of bus types, including parallel ATA (PATA, also called IDE or EIDE; described before the introduction of SATA as ATA), Serial ATA (SATA), SCSI, Serial Attached SCSI (SAS), and Fibre Channel . Bridge circuitry is sometimes used to connect hard disk drives to buses with which they cannot communicate natively, such as IEEE 1394, USB, SCSI and Thunderbolt . </P> <P> Disk drive interfaces have evolved from simple interfaces requiring complex controllers to attach to a computer into high level interfaces that present a consistent interface to a computer system regardless of the internal technology of the hard disk drive . The following table lists some common HDD interfaces in chronological order: </P> <Table> <Tr> <Th> Acronym or abbreviation </Th> <Th> Meaning </Th> <Th> Description </Th> </Tr> <Tr> <Td> SMD </Td> <Td> Storage Module Device </Td> <Td> Bit serial data interface introduced by CDC Standard interface for many mini-computers in the 1970s and 1980s . </Td> </Tr> <Tr> <Td> SASI </Td> <Td> Shugart Associates System Interface </Td> <Td> Word serial interface introduced by Shugart Associates circa 1978; Evolved by ANSI into SCSI (SASI is a compatible subset of the first version of SCSI). </Td> </Tr> <Tr> <Td> ST - 506 ST - 412 ST - 412 RLL </Td> <Td> </Td> <Td> Bit serial data interfaces introduced by Seagate Technology beginning 1980 . Standard interfaces for most small HDDs in the 1980s and early 1990s . </Td> </Tr> <Tr> <Td> SCSI </Td> <Td> Small Computer System Interface </Td> <Td> Word serial interface sponsored by ANSI and introduced in mid 1980s; Standard interfaces for most enterprise HDDs in this century; superseded by SAS </Td> </Tr> <Tr> <Td> ESDI </Td> <Td> Enhanced Small Disk Interface </Td> <Td> Bit serial data interface sponsored by ANSI and first introduced by Maxtor in late 1980s . A higher data rate follow on to the ST - 506 family into the mid-1990s, superseded by SCSI </Td> </Tr> <Tr> <Td> (P) ATA </Td> <Td> (Parallel) AT Attachment </Td> <Td> Word serial interface introduced in late 1980s by Conner Peripherals and subsequently sponsored by ANSI, Successor to ST - 412 / 506 / ESDI . Standard HDD interface on other than enterprise HDDs into this century; superseded by SATA </Td> </Tr> <Tr> <Td> SATA </Td> <Td> Serial ATA </Td> <Td> Bit serial interface successor to PATA sponsored by ANSI and introduced in 2003 . Most common interface for all but enterprise HDDs . </Td> </Tr> <Tr> <Td> SAS </Td> <Td> Serial Attached SCSI </Td> <Td> Bit serial interface successor to SCSI sponsored by ANSI and introduced in 2004 . Most common interface for enterprise HDDs . </Td> </Tr> </Table> <Tr> <Th> Acronym or abbreviation </Th> <Th> Meaning </Th> <Th> Description </Th> </Tr>

Which is not one of the three types of technologies used inside hard drives