The IBM Personal Computer , commonly known as the IBM PC , is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150 , and was introduced on August 12, 1981. It was created by a team of engineers and designers under the direction of Don Estridge of the IBM Entry Systems Division in Boca Raton, Florida.
Alongside "microcomputer" and "home computer", the term "personal computer" was already in use before 1981. It was used as early as 1972 to characterize Xerox PARC's Alto. However, because of the success of the IBM Personal Computer, the term came to mean more specifically a microcomputer compatible with IBM's PC products.
The original line of PCs were part of an IBM strategy to get into the small computer market then dominated by the Commodore PET, Atari 8-bit family, Apple II and Tandy Corporation's TRS-80s, and various CP/M machines. IBM's first desktop microcomputer was the IBM 5100, introduced in 1975. It was a complete system, with a built-in monitor, keyboard, and data storage. It was also very expensive—up to US$20,000. It was specifically designed for professional and scientific problem-solvers, not business users or hobbyists. When the PC was introduced in 1981, it was originally designated as the IBM 5150, putting it in the "5100" series, though its architecture wasn't directly descended from the IBM 5100.
Rather than going through the usual IBM design process, a special team was assembled with authorization to bypass normal company restrictions and get something to market rapidly. This project was given the code name Project Chess at the IBM Entry Systems Division in Boca Raton, Florida. The team consisted of twelve people directed by Don Estridge with Chief Scientist Larry Potter and Chief Systems Architect Lewis Eggebrecht. They developed the PC in about a year. To achieve this they first decided to build the machine with "off-the-shelf" parts from a variety of different original equipment manufacturers (OEMs) and countries. Previously IBM had always developed their own components. Secondly for scheduling and cost reasons, rather than developing unique IBM PC monitor and printer designs, project management decided to utilize an existing "off-the-shelf" IBM monitor developed earlier in IBM Japan as well as an existing Epson printer model. Consequently, the unique IBM PC industrial design elements were relegated to the system unit and keyboard. They also decided on an open architecture, so that other manufacturers could produce and sell peripheral components and compatible software without purchasing licenses. IBM also sold an IBM PC Technical Reference Manual which included complete circuit schematics, a listing of the ROM BIOS source code, and other engineering and programming information. IBM announced the PC on August 12, 1981. Six weeks later at COMDEX Fall, Tecmar had 20 PC products available for sale. These products included memory expansion, IEEE-488, data acquisition and PC Expansion chassis.
At the time, Don Estridge and his team considered using the IBM 801 processor (an early RISC CPU) and its operating system that had been developed at the Thomas J. Watson Research Center in Yorktown Heights, New York. The 801 was at least an order of magnitude more powerful than the Intel 8088, and the operating system many years more advanced than the DOS operating system from Microsoft, that was finally selected. Ruling out an in-house solution made the team’s job much easier and may have avoided a delay in the schedule, but the ultimate consequences of this decision for IBM were far-reaching. IBM had recently developed the Datamaster business microcomputer which used an Intel processor and peripheral ICs; familiarity with these chips and the availability of the Intel 8088 processor was a deciding factor in the choice of processor for the new product. Even the 62-pin expansion bus slots were designed to be similar to the Datamaster slots. Delays due to in-house development of the Datamaster software also influenced the design team to a fast track development process for the PC, with publicly available technical information to encourage third-party developers.
Other manufacturers soon reverse engineered the BIOS to produce their own non-infringing functional copies. Columbia Data Products introduced the first IBM-PC compatible computer in June 1982. In November 1982, Compaq Computer Corporation announced the Compaq Portable , the first portable IBM PC compatible. The first models were shipped in March 1983.
Once the IBM PC became a commercial success, the product came back under the more usual tight IBM management control. IBM's tradition of "rationalizing" their product lines, deliberately restricting the performance of lower-priced models in order to prevent them from "cannibalizing" profits from higher-priced models, worked against them.
Third-party distribution
ComputerLand and Sears Roebuck partnered with IBM from the beginning of development. IBM's head of sales and marketing, H.L. ('Sparky') Sparks, relied on these retail partners for important knowledge of the marketplace.
As a natural progression, Computerland and Sears became the main outlets for the new product. More than 190 Computerland stores already existed, while Sears was in the process of creating a handful of in-store computer centers for sale of the new product. This guaranteed IBM widespread distribution across the United States.
Targeting the new PC at the home market, Sears Roebuck sales failed to live up to expectations. This unfavourable outcome revealed that the original strategy of targeting the office market was the key to higher sales.
Models
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.
PC
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 television set or an RGBI monitor for display; IBM's RGBI monitor was their display model 5153. The other option that was offered by IBM was an MDA (Monochrome Display Adapter) and their monochrome display model 5151. It was possible to install both an MDA and a CGA card and use both monitors concurrently, if supported by the application program. For example, AutoCAD allowed use of a CGA card for graphics and a separate monochrome board for text menus. Some model 5150 PCs with CGA monitors and a printer port also included the MDA adapter by default, because IBM provided the MDA port and printer port on the same adapter card; it was in fact an MDA/printer port combo card.
The most commonly used storage medium was the floppy disk, though cassette tape was originally envisoned by IBM as a low-budget alternative. Accordingly, the IBM 5150 PC was available with one or two floppy drives or without any drives or storage medium; in the latter case IBM intended for a user to connect their own cassette recorder via the 5150's cassette jack. The cassette tape port was mechanically identical to, and located next to, the keyboard port on the 5150's mainboard. A hard disk could not be installed into the 5150's system unit without retrofitting a stronger power supply, but an "Expansion Unit", aka the "IBM 5161 Expansion Chassis" was available, which came with one 10MB hard disk and also allowed the installation of a second hard disk. The system unit had five expansion slots; the expansion unit had eight; however, one of the system unit's slots and one of the expansion unit's slots had to be occupied by the Extender Card and Receiver Card, respectively, which were needed to connect the expansion unit to the system unit and make the expansion unit's other slots available, for a total of 11 slots. however, unlike modern personal computers, some of the slots had to be occupied by display, disk, and I/O adapters, as none of these were available on-board in the 5150; the only on-board external connectors were the keyboard and cassette ports; the simple PC speaker sound hardware was also on-board. The original PC's maximum memory using IBM parts was 256 kiB, 64 kiB on the main board and three 64 kiB expansion cards. The processor was an Intel 8088 (early 1978 version, later were 1978/81/2 versions of intel chip; second-sourced AMDs were used after 1983) running at 4.77 MHz (4/3 the standard NTSC color burst frequency of 3.579545 MHz). Some owners replaced the 8088 with an NEC V20 for a slight increase in processing speed. An Intel 8087 co-processor could also be added for hardware floating-point arithmetic. IBM sold the PC in configurations with 16 kiB or 64 kiB of RAM preinstalled using either nine or thirty-six 16-kibit DRAM chips. (As was common at the time, a ninth bit was used for parity checking of memory.)
Although the TV-compatible video board, cassette port and FCC Class B certification were all aimed at making it a home computer, the original PC proved too expensive for the home market. At introduction a PC with 64 kiB of RAM and a single 5 1/4 inch floppy drive and monitor sold for US $3,005, while the cheapest configuration ($1,565) that had no floppy drives, only 16kiB RAM, and no monitor (again, under the expectation that users would connect their existing TV sets and cassette recorder
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