IBM 650
IBM 650
The IBM 650 was the Model T of computing — the first computer mass-produced, nearly 2,000 systems built between 1954 and 1962, and the first to make a meaningful profit. At a fraction of the 701's price it brought computing within reach of small businesses and universities; the first unit went to John Hancock Mutual Life Insurance in Boston in December 1954, and by decade's end the 650 was the most popular computer on Earth.[1]
The hardware was a study in squeezing a computer onto a drum: a two-address, bi-quinary coded decimal machine — addresses and data both decimal — running digit-serial at 125 kHz, with its 4,000-word drum spinning at 12,500 rpm. Every operation's cost depended on drum geography, so the 650's culture made "optimum programming" an industry: the famous SOAP assembler (Symbolic Optimal Assembly Program) existed largely to place instructions where the rotating memory would find them fastest. And because it was cheap enough to teach on, the 650 became the machine a generation learned programming on — a rotating drum full of a decade's first programs.[2]
The computer Knuth remembered in stone
The 650's place in culture is literally inscribed: The Art of Computer Programming's dedication reads "This series of books is affectionately dedicated to the Type 650 computer once installed at Case Institute of Technology, in remembrance of many pleasant evenings" — Knuth learned programming on a 650 and immortalized the machine in the field's bible. Others cut teeth the same way: the 650 at a university was often the first computer anyone on campus had ever touched.[3]
Where it sits
The 650 is the proof that cheap was a feature: it wasn't fast (adds took up to 10 ms), but it was there — in insurance offices, engineering shops, and campuses — where nothing else was. It created the mass market IBM would dominate for fifty years, and the first generation of programmers who learned that a computer was something you could actually get your hands on.
Check your understanding
- What made the 650 the "Model T" of computing — two production firsts?
- What was bi-quinary coding — and what did the drum's rotation have to do with programming?
- What was SOAP, and why "Optimal"?
- How is the 650 memorialized in computer science's most famous book series?
Show answers
1 — first mass-produced computer (~2,000 units) and the first to make a meaningful profit. 2 — bi-quinary decimal encoding for data and addresses; instruction timing depended on where data sat on the rotating drum — placement was the optimization. 3 — Symbolic Optimal Assembly Program — its job included placing instructions optimally on the drum. 4 — Knuth **dedicated The Art of Computer Programming** to the 650 at Case Institute of Technology, "in remembrance of many pleasant evenings."
Footnotes
- ↑ IBM 650 and Columbia's ACIS history — the ~2,000 units, the John Hancock first install, and the mass-production firsts
- ↑ IBM 650 — the bi-quinary decimal design, drum specs, and SOAP's optimal-placement mandate
- ↑ Knuth, The Art of Computer Programming dedication — the Case Institute 650 memorialized; see also IBM 650