IBM PC/AT

IBM PC/AT. Introduced in August 1984, the IBM Personal Computer/Advanced Technology was a landmark model in the IBM Personal Computer family, representing a major leap in performance and capability. It established the Intel 80286 microprocessor and the 16-bit ISA bus as dominant standards for business computing throughout the mid-to-late 1980s. Its robust architecture and enhanced storage defined a new generation of IBM-compatible machines from competitors like Compaq, AST Research, and Dell.

History and development

Development of the system, codenamed "PC/AT" for Advanced Technology, began at IBM's Entry Systems Division in Boca Raton, Florida, following the success of the IBM PC/XT. The project aimed to create a high-performance machine for multi-user and demanding business applications, leading to the selection of the new Intel 80286 processor. Key engineers, including Philip Don Estridge, leveraged lessons from earlier projects like the IBM 3270 PC to design a more expandable platform. Its announcement in 1984 was a major event in the history of computing, directly challenging rivals like the Apple Macintosh and various UNIX workstations from Sun Microsystems and Apollo Computer.

Technical specifications

At its core was the Intel 80286 CPU, initially running at 6 MHz and later at 8 MHz, which supported Protected mode for advanced multitasking, though this was rarely used by MS-DOS. It featured a true 16-bit data path via its AT bus (later called ISA), which became an industry standard. Standard memory was 256 KB, expandable via proprietary memory cards to 16 MB. Storage was revolutionized by an internal 20 MB Hard disk drive (model 0671 from IBM Rochester) and a high-density 1.2 MB 5.25-inch floppy drive. Graphics were supported by MDA, CGA, and the new EGA, while connectivity included serial and parallel ports.

Models and variants

The original Model 5170 was released in 1984, followed by revised versions in 1985 and 1986 that increased the processor speed to 8 MHz and offered different hard disk configurations. While IBM manufactured the flagship systems, the architecture's openness led to a vast market for "AT-compatible" clones from companies such as Compaq (the Compaq Deskpro 286), Tandy, Zenith Data Systems, and Hewlett-Packard. IBM also produced specialized variants, including the IBM 3270 PC/AT for mainframe connectivity and the ruggedized IBM 7531 Industrial Computer. Later, the platform was effectively succeeded by systems using the Intel 80386 and the PS/2 line.

Impact and legacy

The system's architecture defined the "AT standard," making the 16-bit ISA bus and 286 processor the baseline for business PCs for years, profoundly shaping the clone market and consolidating the dominance of the Wintel platform. Its design influenced subsequent standards like EISA and even aspects of the Micro Channel architecture in the PS/2. The term "AT" became a universal marketing label for advanced clones, and its physical layout influenced case designs for a generation. It enabled more sophisticated software from companies like Lotus, Ashton-Tate, and Autodesk, accelerating the move of business functions from minicomputers to the desktop.

Software and operating systems

It shipped with PC DOS 3.0, which added support for the 1.2 MB floppy drive and larger hard disks. The hardware's capabilities encouraged development for Windows 1.0 and later OS/2, a joint project of IBM and Microsoft. Its Protected mode allowed it to run multi-user UNIX-like systems such as Xenix from Microsoft and IBM PC/IX. Major business applications like Lotus 1-2-3 version 2.0, dBASE III from Ashton-Tate, and early versions of WordPerfect were optimized for its power. This software ecosystem cemented its role as the premier platform for business computing until the rise of the Intel 80386.

Category:IBM personal computers Category:1984 introductions Category:Discontinued computers