Apple started using the less-expensive parallel ATA (PATA, also known as IDE) for its low-end machines with the Macintosh Quadra 630 in 1994, and added it to its high-end desktops starting with the Power Macintosh G3 in 1997.
Apple dropped on-board SCSI completely in favor of IDE and Fire Wire with the (Blue & White) Power Mac G3 in 1999, while still offering a PCI SCSI host adapter as an option on up to the Power Macintosh G4 (AGP Graphics) models.
The SCSI standards define commands, protocols, electrical and optical interfaces.
SCSI is most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices.
The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements. Further refinements have resulted in improvements in performance and support for ever-increasing storage data capacity.
The ancestral SCSI standard, X3.131-1986, generally referred to as SCSI-1, was published by the X3T9 technical committee of the American National Standards Institute (ANSI) in 1986. A SASI controller provided a bridge between a hard disk drive's low-level interface and a host computer, which needed to read blocks of data.
SCSI interfaces have often been included on computers from various manufacturers for use under Microsoft Windows, classic Mac OS, Unix, Commodore Amiga and Linux operating systems, either implemented on the motherboard or by the means of plug-in adaptors.
With the advent of SAS and SATA drives, provision for parallel SCSI on motherboards was discontinued.Instead of SCSI, modern desktop computers and notebooks typically use SATA interfaces for internal hard disk drives, with M.2 and PCIe gaining popularity as SATA can bottleneck modern solid-state drives. The first was parallel SCSI (also called SCSI Parallel Interface or SPI), which uses a parallel bus design.Since 2005, SPI was gradually replaced by Serial Attached SCSI (SAS), which uses a serial design but retains other aspects of the technology.Almost a full day was devoted to agreeing to name the standard "Small Computer System Interface", which Boucher intended to be pronounced "sexy", but ENDL's The "small" reference in "small computer system interface" is historical; since the mid-1990s, SCSI has been available on even the largest of computer systems.Since its standardization in 1986, SCSI has been commonly used in the Amiga, Atari, Apple Macintosh and Sun Microsystems (now part of Oracle Corporation) computer lines and PC server systems.SASI controller boards were typically the size of a hard disk drive and were usually physically mounted to the drive's chassis.