The PDP-4 was the successor to the

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 ...

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 ...

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 the price of its predecessor. All later 18-bit PDP machines ( 7, 9 and 15) are based on a similar, but enlarged

instruction set In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, s ...

, more powerful than, but based on the same concepts as, the 12-bit

PDP-5 The PDP-5 was Digital Equipment Corporation's first 12-bit computer, introduced in 1963. History An earlier 12-bit computer, named LINC has been described as the first minicomputer and also "the first modern personal computer." It had 2,048 1 ...

PDP-8 The PDP-8 is a family of 12-bit minicomputers that was produced by Digital Equipment Corporation (DEC). It was the first commercially successful minicomputer, with over 50,000 units sold during the model's lifetime. Its basic design follows the pi ...

series. Approximately 54 were sold.

Hardware

The system's memory cycle is 8 microseconds, compared to 5 microseconds for the PDP-1. The PDP-4 weighs about .

Mass storage

Both the

and the PDP-4 were introduced as

paper tape Five- and eight-hole wide 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 st ...

-based systems. The only use, if any, for IBM-compatible 200 BPI or 556 BPI

magnetic tape Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnetic ...

was for data. The use of "mass storage" drums - not even a

megabyte The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix ''mega'' is a multiplier of (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes ...

and non-removable - were an available option, but were not in the spirit of the “personal” or serially shared systems that DEC offered. It was in this setting that DEC introduced DECtape, initially called "MicroTape", for both the PDP-1 and PDP-4.

Software

DEC provided an editor, an assembler, and a FORTRAN II compiler. The assembler was different from that of the PDP-1 in two ways: * Unlike the PDP-1, macros were not supported. * It was a one-pass assembler; paper-tape input did not have to be read twice.

Photos

PDP-4

References