The PDP-9, the fourth of the five 18-bit

minicomputer A minicomputer, or colloquially mini, is a class of smaller general purpose computers that developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, ...

s produced by

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...

, was introduced in 1966. A total of 445 PDP-9 systems were produced, of which 40 were the compact, low-cost PDP-9/L units..

History

The 18-bit PDP systems preceding the PDP-9 were the

PDP-1 The PDP-1 (''Programmed Data Processor-1'') is the first computer in Digital Equipment Corporation's PDP series and was first produced in 1959. It is famous for being the computer most important in the creation of hacker culture at Massachusetts ...

PDP-4 The PDP-4 was the successor to the Digital Equipment Corporation's PDP-1. History This 18-bit machine, first shipped in 1962, was a compromise: "with slower memory and different packaging" than the PDP-1, but priced at $65,000 - less than half th ...

and

PDP-7 The PDP-7 was a minicomputer produced by Digital Equipment Corporation as part of the PDP series. Introduced in 1964, shipped since 1965, it was the first to use their Flip-Chip technology. With a cost of , it was cheap but powerful by the s ...

. Its successor was the

PDP-15 The PDP-15 was the fifth and last of the 18-bit minicomputers produced by Digital Equipment Corporation. The PDP-1 was first delivered in December 1959 and the first PDP-15 was delivered in February 1970. More than 400 of these successors to t ...

Hardware

The PDP-9, which was "two metres wide and about 75cm deep," was approximately twice the speed of the PDP-7. It was built using discrete transistors, and had an optional integrated

vector graphics Vector graphics is a form of computer graphics in which visual images are created directly from geometric shapes defined on a Cartesian plane, such as points, lines, curves and polygons. The associated mechanisms may include vector display a ...

terminal. The PDP-9 weighed about and the PDP-9/L weighed about . It was DEC's first microprogrammed machine. A typical configuration included: * 300 cps

Paper Tape Five- and eight-hole punched paper tape Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated paper tape is a form of data storage ...

Reader * 50 cps Paper Tape Punch * 10 cps Console Teleprinter, Model 33 KSR Teletype-IMG 7287

Among the improvements of the PDP-9 over its PDP-7 predecessor were: * the addition of Status flags for reader and punch errors, thus providing added flexibility and for error detection * an entirely new design for multi-level interrupts, called the Automatic Priority Interrupt (API) option * a more advanced form of memory management User/university-based research projects for extending the PDP-9 included: * a hardware capability for floating point arithmetic, at a time when machines in this price range used software * a PDP-9 controlled parallel computer

Software

The system came with a single-user Keyboard monitor. DECsys, provided an interactive, single user, program development environment for Fortran and assembly language programs. Both FORTRAN II and FORTRAN IV were implemented for the PDP-9.

MUMPS MUMPS ("Massachusetts General Hospital Utility Multi-Programming System"), or M, is an imperative, high-level programming language with an integrated transaction processing key–value database. It was originally developed at Massachusetts Gener ...

was originally developed on the PDP-7, and ran on several PDP-9s at the

Massachusetts General Hospital Massachusetts General Hospital (Mass General or MGH) is the original and largest teaching hospital of Harvard Medical School located in the West End neighborhood of Boston, Massachusetts. It is the third oldest general hospital in the United Stat ...

Sales

The

, of which 120 were sold, was described as "highly successful.". The PDP-9 sold 445 units. Both had submodels, the PDP-7Asometimes identified by customers and media as PDP-7/A and the PDP-9/L,yes, DEC had a "slash" for the 9/L but not for the 7A neither of which accounted for a substantial percentage of sales.directly mentioned for one, calculated in the other case

Notes

References