Don Estridge

На каждую хорошую мысль неизбежно находится свой дурак, аккуратно доводящий её до абсурда.
Илья Ильф

Don Estridge and the IBM PC
Don Estridge (1937-1985) and the IBM PC in 1982

The biggest computer manufacturer in the world—IBM, was in a difficult situation in the 1970s. Despite IBM’s strategy and multimillion efforts to get into the small computer market, it was dominated by the Commodore PET, Atari 8-bit family, Apple II, and TRS-80, as well as various CP/M machines.

IBM dominated the market of mini, middle-range, and mainframe computers, but didn’t achieve even a small success in the very perspective microcomputers market. 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, but it was very expensive—up to $20000, so it didn’t achieve market success. It was specifically designed for professional and scientific problem-solvers, not business users or hobbyists. Gradually IBM management began thinking of producing microcomputers as a profitable business.

When the IBM PC was introduced in mid-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. The IBM PC was created by a team of several IBM engineers and designers under the direction of Don Estridge, the director of the IBM Entry Systems Division in Boca Raton, Florida. Starting in mid-1980, in just four months Estridge and his team developed a prototype and within one year the IBM PC was on retail shelves, a record time for product development in the giant company.

After hesitation between the Intel 8086 and the Motorola MC68000 (16-bit CPUs), they decided to use the Intel 8088 (8/16-bit) processor, as the two other ones were considered too powerful 🙂 Then they asked Digital Research (the creators of CP/M) to create an operating system for their new computer, but as DR was not very interested, they then asked a small company (known for its BASIC Programming Language, first used in Altair 8800) to write the operating system: Microsoft.

Microsoft wasn’t capable of doing it in the given timeframe, so its owner Bill Gates bought the rights to a small, hacked OS written by a small company called Seattle Computer Products: QDOS (which reportedly stood for “Quick and Dirty Operating System”, which itself bears a striking resemblance to CP/M) which became PC-DOS and then later MS-DOS. In fact, when IBM PC was launched, three operating systems could run on it: PC-DOS, CPM-86, but also the UCSD D-PASCAL system.

The original IBM PC wasn’t very powerful (and was certainly less powerful than a lot of 8-bit computers at the time). The very first PCs had only 16 KB RAM and no floppy disk units, they used cassettes to load and store programs (notice that the commands to handle the cassette drives were present in the operating system all the way up to MS-DOS 5). In fact, units could also be purchased from IBM with drives and more RAM. Only the lowest-cost version had no drives included (this is exactly how Atari, Apple, and the other manufacturers did it as well).

IBM PC Model 5150 with two 160 KB 5.25” floppy disk drives
IBM PC Model 5150 with two 160 KB 5.25” floppy disk drives

The model 5150 (see the nearby image) was introduced in August 1981 (see the IBM Personal Computer brochure). The system unit was a box with a size 50.8 (W) x 40.6 (D) x 14 (H) cm, with a built-in 63.5W switching power supply unit. It featured Intel 8008 CPU, working at a speed of 4.77 MHz, and an optional math co-coprocessor 8087. The RAM was 64 KB (the very first ones had only 16 KB), 256 KB max. (then later 640 KB max.) The ROM was 64 KB, including built-in language IBM BASIC (Special Microsoft BASIC-80 version). The keyboard was a full stroke ‘clicky’ 83 keys with 10 function keys and a numeric keypad. The display was monochrome, working in text mode: (40 or 80 char x 25 lines) or 2 CGA graphic modes: (320 x 200 and 640 x 200). The sound was a tone generator with a built-in speaker. The I/O ports were five internal 8-bit ISA slots, monitor, parallel (Centronics), and cassette. The built-in media was one or two 160 KB 5.25” floppy disk drives. Three OSs were provided—MS-DOS, CP/M-86, and USCD Pascal.

Although the IBM PC XT was launched in 1983 (the first IBM PC to come with an internal hard drive as standard), and IBM AT was launched in 1984 (with the new Intel 80286 CPU), IBM continued production of the original PC in various configurations, for several years. The model types were followed by an xx version number, i.e. 5150-xx, where the xx represented the included options (amount of RAM, single or dual floppy disk drive, etc.)

IBM PC 5150 became actually a success due to the name and fame of IBM, high-quality construction (especially the keyboard and monitor), great expandability, and IBM’s decision to publish complete technical specs. The IBM PC Technical manual included circuit diagrams and the full source code for the BIOS. While the original IBM PC technology is largely obsolete by today’s standards, many are still in service. As of June 2006, IBM PC and XT models were still in use at the majority of U.S. National Weather Service upper-air observing sites. The computers were used to process data as it is returned from the ascending radiosonde, attached to a weather balloon. Factors that have contributed to the 5150 PC’s longevity are its flexible modular design, open technical standard making information needed to adapt, modify, and repair it readily available, use of few special nonstandard parts, and rugged high-standard IBM manufacturing, the last of which provided for exceptional long-term reliability and durability. Most newer PCs, by contrast, use special-purpose chips (ASICs) implementing trend-driven technology which becomes obsolete in a few years, after which the parts become unavailable.

Biography of Don Estridge

Philip Donald “Don” Estridge (1937-1985)
Philip Donald “Don” Estridge (1937-1985)

Philip Donald “Don” Estridge, known as the “father of the IBM PC”, was born on 23 June 1937 in Jacksonville, Florida. He was the son of Lucius Luther Estridge Jr. (1908-1983), and Marie Isabel DeHoff Estridge (1907-1973), who married in 1935. Lucius held a BA degree from the University of Florida, was a chief clerk of the office of the work progress administration in Orlando, FL, and was a professional photographer. Marie was a graduate of St. Joseph’s Academy.

From 1942 to 1951, Don attended St. Paul’s School in Jacksonville from Kindergarten through the Eight grade. Then he graduated from Bishop Kenny High School in 1955 and completed a bachelor’s degree in electrical engineering at the University of Florida in 1959. Don joined IBM in June 1959 as a junior engineer in Kingston, New York, and held various positions in the Federal Systems Division, including working on the manned and unmanned programming support for NASA/Goddard. In 1969 he joined the General Systems Division and from 1975 to 1979 he was the Series/1 (a mini computer) programming manager. During 1979-1980, he had responsibility for the development of a Series/1 integrated product.

Don became manager of Entry Level Systems at IBM in 1980, responsible for the development of small microprocessor-based systems for tiny business and personal use, with a team of just 14 people and a revenue base of zero. By the time he gave up leading IBM’s PC division in 1985, the division had 10000 employees and annual revenue of $4.5 billion. After the extraordinarily successful development of the IBM PC, Estridge was promoted several times at IBM and in 1984 became Vice President, Manufacturing. In 1983 he turned down a lucrative multimillion-dollar offer from Steve Jobs to become President of Apple Computers.

Don married Mary Ann Hellier (1939-1985), a piano teacher, on 13 September 1958. Three children would eventually be born from his marriage: Patricia Ann, Mary Evelyn, and Sandra Marie.

Don and his wife, Mary Anne, were two of the 137 victims on board Delta Air Lines Flight 191, which crashed as it attempted to land during a storm in Dallas, Texas on 2 August 1985. It was a huge blow to IBM because, besides Estridge and his wife, they lost five other employees, six other family members of IBM employees, and two IBM summer interns.