Editing IBM Personal Computer AT (section)

== Clones ==
The PC AT architecture was functionally an open design, and IBM's efforts to [[trademark]] the AT name largely failed. Many 286-based PCs were modeled after it and marketed as ''AT-compatible''. The label also became a standard term in reference to PCs that used the same type of power supply, case, and motherboard layout as the 5170. ''AT-class'' became a term describing any machine which supported the same BIOS functions, 80286 or greater processor, 16-bit expansion slots, keyboard interface, 1.2&nbsp;MB {{frac|5|1|4}} inch floppy disk drives and other defining technical features of the IBM PC AT.

Large companies that had been late to release PC compatibles rushed out AT compatibles, with an estimated 100,000 sold by the end of 1985.<ref name="bright19860623">{{Cite magazine |last=Bright |first=David |date=1986-06-23 |title=AT compatibles: Systems vendors push to give single-source option |url=https://books.google.com/books?id=mop2UUCt4kIC&pg=PA1#v=onepage&q&f=true |access-date=2025-05-17 |magazine=Computerworld |pages=1, 14-15 |volume=XX |issue=25}}</ref> In the United States, popular brands of AT clones included the [[Tandy 3000]], [[Compaq Deskpro]] 286, [[Hewlett-Packard|HP]] Vectra,<ref>{{cite web |title=HP Computer Museum |url=http://hpmuseum.net/display_item.php?hw=125 |website=hpmuseum dot net |publisher=BGImages Australia |access-date=July 9, 2020}}</ref> [[Zenith Data Systems#Computers|Zenith]] Z-286,<ref>{{cite magazine |title=Zenith Innovates Again |magazine=PC Magazine |date=August 1989 |page=375 |url=https://books.google.com/books?id=fSMW_RgWwIgC&q=zenith+z-286&pg=PT362 |via=Google Books |author=Zenith Data Systems}}</ref> [[Epson Equity]] Models II+<ref>{{cite web |title=Equity II+ Product Info |url=https://files.support.epson.com/pdf/e2p___/e2p___pg.pdf |website=files.support.epson.com |publisher=Epson USA |access-date=July 8, 2020}}</ref> and III,<ref>{{cite web |title=Equity III Product Info |url=http://files.support.epson.com/pdf/e3p___/e3p___pg.pdf|website=files.support.epson.com |publisher=Epson USA |access-date=July 8, 2020}}</ref> and [[Commodore PC compatible systems#Models|Commodore PC-30 and PC-40]]. In Europe, on the other hand, most AT-clones sold were more or less anonymous.

The AT bus became the de facto ISA ([[Industry Standard Architecture]]), while PC XT slots were retroactively named ''8-bit ISA''. The disk interface for the AT, originally a Seagate [[ST506]] compatible interface on IBM's disk controller card, was updated and standardized as ATA ("AT Attachment") by [[Western Digital]] and [[Compaq]] in 1986, and later renamed PATA ([[Parallel ATA|Parallel AT Attachment]]). The ATA interface was also known as IDE, because the drive controller, instead of being on the interface card, was integrated into the drive ([[Parallel ATA#IDE and ATA-1|Integrated Drive Electronics]]).