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

minicomputer A minicomputer, or colloquially mini, is a type of general-purpose computer mostly developed from the mid-1960s, built significantly smaller and sold at a much lower price than mainframe computers . By 21st century-standards however, a mini is ...

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 until ...

, 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 are 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 known for being the most important computer in the creation of hacker culture at the Massachusetts ...

, PDP-4 and PDP-7. Its successor is the PDP-15.

Hardware

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

vector graphics Vector graphics are 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 displ ...

terminal. The PDP-9 has a memory cycle time of 1 microsecond, and weighs about . The PDP-9/L has a memory cycle time of 1.5 microseconds, and weighs about . It is DEC's first microprogrammed machine. A typical configuration included: * 300 cps paper tape reader * 50 cps paper tape punch * DECtape for operating system and user files * 10 cps console teleprinter, Model 33 KSR Teletype-IMG 7287

Among the improvements of the PDP-9 over its PDP-7 predecessor are: * 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 include: * a hardware capability for

floating-point arithmetic In computing, floating-point arithmetic (FP) is arithmetic on subsets of real numbers formed by a ''significand'' (a Sign (mathematics), signed sequence of a fixed number of digits in some Radix, base) multiplied by an integer power of that ba ...

, at a time when machines in this price range used software for floating-point arithmetic * a PDP-9 controlled parallel computer

Software

The system came with an OS that functions as single-user keyboard monitor, called ADSS (ADvanced Software System). 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 Gen ...

was originally developed on the PDP-7, and ran on several PDP-9s at the Massachusetts General Hospital.

Sales

The PDP-7, of which 120 were sold, was described as "highly successful". The PDP-9 sold 445 units. Both have 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