At the time, Don Estridge and his team considered using the 801 processor and its operating system that had been developed at the IBM research laboratory in Yorktown Heights, New York (The 801 was an early RISC microprocessor designed by John Cocke and his team at Yorktown Heights.) 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 were 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 disastrous.
Unfortunately for IBM, other manufacturers rapidly reverse engineered the BIOS to produce their own royalty-free versions. Columbia Data Products produced the Multi Personal Computer, the first IBM-PC compatible computer. Compaq Computer Corporation announced the first portable IBM PC compatible in November 1982 (it did not ship until March 1983) - the Compaq Portable.
Once the IBM PC became a commercial success the PC came back under the usual IBM management control, with the result that competitors had little trouble taking the lead from them. (In this regard, 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).
As of June 2006, IBM PC and XT models are still in use at the majority of U.S. National Weather Service upper-air observing sites. The computers are used to process data as it is returned from the ascending radiosonde, attached to a weather balloon. They are being phased out over a several year period, to be replaced by the Radiosonde Replacement System.
The first IBM PC was released on August 12, 1981. Although not cheap, at a base price of $1,565 (around $3,500 in 2006 figures) it was affordable for businesses - and it was business that purchased the PC. However it was not the corporate "computer department" that was responsible for this, for the PC was not seen as a 'proper' computer. It was generally well educated middle managers that saw the potential - once the revolutionary VisiCalc spreadsheet, the "killer app", had been ported to the PC as a feature of Lotus 1-2-3. Reassured by the IBM name, they began buying the machines on their own budgets to help do the calculations they had learned at business school.
IBM PC models
The models of IBM's first-generation Personal Computer (PC) series have names:
The second generation 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.
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.
The main circuit board in an IBM PC is called the motherboard. This carries the CPU and memory, and has a bus with slots for expansion cards.
The bus used in the original PC became very popular, and was subsequently named ISA. It is in use to this day in computers for industrial use. Later, requirements for higher speed and more capacity forced the development of new versions. IBM introduced the MCA bus with the PS/2 line. The VESA Local Bus allowed for up to three, much faster 32-bit cards, and the EISA architecture was developed as a backward compatible standard including 32-bit card slots, but it only sold well in high-end server systems. The lower-cost and more general PCI bus was introduced in 1994 and has now become ubiquitous.
The motherboard is connected by cables to internal storage devices such as hard disks, floppy disks and CD-ROM drives. These tend to be made in standard sizes, such as 3.5" (90 mm) and 5.25" (133.4 mm) widths, with standard fixing holes. The case also contains a standard power supply unit (PSU) which is either an AT or ATX standard size.
Intel 8086 and 8088-based PCs require EMS (expanded memory) boards to work with more than one megabyte of memory. The original IBM PC AT used an Intel 80286 processor which can access up to 16 megabytes of memory (though standard DOS applications cannot use more than one megabyte without using additional APIs.) Intel 80286-based computers running under OS/2 can work with the maximum memory.
The original 1981 IBM PC's keyboard was severely criticised by typists for its non-standard placement of the return and left shift keys. In 1984, IBM corrected this on its AT keyboard, but shortened the backspace key, making it harder to reach. In 1987, it introduced the enhanced keyboard, which relocated all the function keys and the Ctrl keys. The Esc key was also relocated to the opposite side of the keyboard.
An "IBM PC compatible" may have a keyboard which does not recognize every key combination a true IBM PC does, e.g. shifted cursor keys. In addition, the "compatible" vendors sometimes used proprietary keyboard interfaces, preventing the keyboard from being replaced.
The original IBM PC used the 7-bit ASCII alphabet as its basis, but extended it to 8 bits with nonstandard character codes. This character set was not suitable for some international applications, and soon a veritable cottage industry emerged providing variants of the original character set in various national variants. In IBM tradition, these variants were called code pages. These codings are now obsolete, having been replaced by more systematic and standardized forms of character coding, such as ISO 8859-1, Windows-1251 and Unicode.
Officially, the standard storage medium for the original IBM PC model 5150 was a cassette drive. Technologically obsolete even by 1981 standards, it was seldom used, and few (if any) IBM PCs left the factory without a floppy disk drive installed. The 1981 PC had one or two 180 kilobyte 5¼ inch single-sided double-density floppy disk drives; XTs generally had one double-sided 360 kB drive (next to the hard disk).
The first IBM PC that included a fixed, non-removable, hard disk was the XT. Hard disks for IBM compatibles soon became available with very large storage capacities. If a hard disk was added that was not compatible with the existing disk controller, a new controller board had to be plugged in; some disks were integrated with their controller in a single expansion board, commonly called a "Hard Card".
In 1984, IBM introduced the 1.2 megabyte dual sided floppy disk along with its AT model. Although often used as backup storage, the high density floppy was not often used for interchangeability. In 1986, IBM introduced the 720 kB double density 3.5" microfloppy disk on its Convertible laptop computer. It introduced the 1.44 MB high density version with the PS/2 line. These disk drives could be added to existing older model PCs. In 1988 IBM introduced a drive for 2.88 MB "DSED" diskettes in its top-of-the-line models; it was an instant failure and is all but forgotten today (but survives as a possible "size" choice in disk-formatting utilities).
All IBM PCs includes a relatively small piece of software stored in ROM. The original IBM PC 40 kB ROM included 8 kB for power-on self-test (POST) and basic input/output system (BIOS) functions plus 32 kB BASIC in ROM (Cassette BASIC). The ROM BASIC interpreter was the default user interface if no DOS boot disk was present. BASICA was distributed on floppy disk and provided a way to run the ROM BASIC under PC-DOS control.
Much of the original development team, including Don Estridge, perished on August 2, 1985 during the crash of Delta Air Lines Flight 191. As a result of this disaster, IBM and many other companies set limits on the number of employees allowed on a single flight.