IBM PC

IBM PC™ (Personal Computer), is a trademark of IBM. The predecessor of the current personal computers and progenitor of the IBM PC compatible hardware platform, it was introduced in August 1981. The original model was designated the IBM 5150. It was created by a team of 12 engineers and designers under the direction of Don Estridge of the IBM Entry Systems Division. The introduction of the PC changed the world of IBM in 1981.

IBM PC models

The models of IBM's first-generation Personal Computer (PC) series have names:

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• The original PC had a version of Microsoft BASIC —IBM Cassette BASIC— in ROM. The CGA (Color Graphics Adapter) video card could use a standard TV for display. The standard storage device was cassette tape. A floppy disk drive was an optional extra; no hard disk was available. It had only five expansion slots; maximum memory using IBM parts was 256 KB, 64K on the main board and three 64K expansion cards. The processor was an Intel 8088 (second-sourced AMDs were used after 1983) running at 4.77 MHz. IBM sold it in configurations with 16K and 64K of RAM preinstalled.
• The original PC failed miserably in the home market, but was widely used in business. The "IBM Personal Computer XT" was an enhanced machine designed for business use. It had 8 expansion slots and a 10 megabyte hard disk. It could take 256K of memory on the main board; later models were expandable to 640K, which combined with the ROM made up the full megabyte of memory that the 8088 could address. It was usually sold with a Monochrome Display Adapter (MDA) video card. The processor was still a 4.77 MHz Intel 8088 and the expansion bus still 8-bit ISA with XT bus architecture.
• The "IBM Personal Computer/AT", announced August 1984, used an Intel 80286 processor, originally at 6 MHz. It had a 16-bit ISA bus and 20MB harddrive. A faster model, running at 8 MHz, was introduced in 1986. IBM made some attempt at marketing it as a multi-user machine, but it sold mainly as a faster PC for power users. Early PC/ATs were plagued with reliability problems, mostly related to the internal 20 MB hard drive. While some people blamed IBM's controller card and others blamed the hard drive manufacturer (Computer Memories International, or CMI), the IBM controller card worked fine with other drives, including CMI's 33-megabyte model. The problems introduced doubt about the computer and, for a while, even about the 286 architecture in general, but after IBM replaced the 20-megabyte CMI drives, the PC/AT proved reliable and became a lasting industry standard. CMI quickly went out of business.
• IBM Convertible
• IBM Portable
• IBM PCjr

The models of its second generation, the IBM Personal System/2 (PS/2), are known by model number: Model 25, Model 30. Within each series, the models are also commonly referenced by their CPU clock rate.

Related Topics:
IBM Personal System/2 - Model 25 - Model 30 - CPU clock rate

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All IBM personal computers are software compatible with each other in general, but not every program will work in every machine. Some programs are time sensitive to a particular speed class. Older programs will not take advantage of newer higher-resolution display standards.

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