SCSI cable assemblies are used for high-speed bus connections between small computers and intelligent peripherals such as hard disks, printers, and optical disks. There are many different small computer system interface (SCSI) standards. Choices include: SCSI-1, SCSI-2, and SCSI-3; Fast SCSI, Wide SCSI, and Fast Wide SCSI; Ultra SCSI, Ultra2 SCSI, and Ultra3 SCSI; Ultra 320 SCSI and Ultra 640 SCSI; Wide Ultra SCSI and Wide Ultra 2 SCSI; Fibre Channel and Serial SCSI. SCSI-1 allows asynchronous data transfer rates of 1.5 Mbps and synchronous transfer rates up to 5 Mbps. SCSI-2 provides significant improvements over SCSI-1, including faster data transfer rates, better connectors, a wider bus path, parity checking, and better reliability via synchronous negotiation. Fast SCSI has a bus speed of 10 MHz and a maximum data transfer rate (10 Mbps) that is twice as fast as SCSI-1 (5 Mbps). Wide SCSI has a bus speed of 10 MHz and a bus width (16 bits) that is twice as fast as SCSI-1. Fast Wide SCSI has a maximum data transfer rate of 20 Mbps and a bus width of 16 bits. Ultra SCSI or Fast-20 has a bus speed of 20 MHz. Ultra2 SCSI or Fast-40 has a bus speed of 40 MHz. Ultra3 SCSI (Fast-80, Ultra160) has a bus speed of 80 MHz. Ultra320 SCSI (320 Mbps), Ultra 640 SCSI (640 Mbps), and Wide Ultra SCSI (40 Mbps) differ in terms of maximum data rate for the wide (16-bit) bus. SCSI cable assemblies that use Fibre Channel and Serial SCSI, a subset of FireWire (Apple Computer, Inc.), are also available.