The various PDP machines can generally be grouped into families based on
word length and
backward compatibility. Families of PDP machines include: although those machines were not compatible with the PDP-1. ;PDP-2: A number reserved for an unbuilt, undesigned 24-bit design. ;PDP-3: First DEC-designed (for US "
black budget" outfits) 36-bit machine, though DEC did not offer it as a product. The only PDP-3 was built from DEC modules by the
CIA's Scientific Engineering Institute (SEI) in
Waltham, Massachusetts to process
radar cross section data for the
Lockheed A-12 reconnaissance aircraft in 1960. of which "approximately 54 were sold" was a compromise: "with slower memory and different packaging" than the PDP-1, but priced at $65,000 - considerably less than its predecessor (about half the price). The PDP-9 established
minicomputers as the leading edge of the computer industry. ;
PDP-10: Also marketed as the DECsystem-10, this 36-bit timesharing machine (1966) was quite successful over several different implementations (KA, KI, KL, KS) and models. The instruction set is a slightly elaborated form of that of the PDP-6. :The KL was also used for the
DECSYSTEM-20. The KS was used for the 2020, DEC's entry in the
distributed processing market, introduced as "the world's lowest cost mainframe computer system." ;
PDP-11: The archetypal minicomputer (1970); a 16-bit machine and another commercial success for DEC. The
LSI-11 is a four-chip PDP-11 used primarily for
embedded systems. The 32-bit
VAX series is descended from the PDP-11, and early VAX models have a PDP-11 compatibility mode. The 16-bit PDP-11 instruction set has been very influential, with processors ranging from the
Motorola 68000 to the
Renesas H8 and
Texas Instruments MSP430, inspired by its highly
orthogonal, general-register oriented
instruction set and rich
addressing modes. The PDP-11 family was extremely long-lived, spanning 20 years and many different implementations and technologies. ;
PDP-12: 12-bit machine (1969), descendant of the LINC-8 and thus of the PDP-8. It had one CPU that could change modes and execute the instruction set of either system. See
LINC and PDP-12 User Manual. With slight redesign, and different livery, officially followed by, and marketed as, the "Lab-8". ;PDP-13: Designation was not used. ;
PDP-14: A machine with 12-bit instructions, intended as an industrial controller (
PLC; 1969). It has no data memory or data registers; instructions can test Boolean input signals, set or clear Boolean output signals, jump conditional or unconditionally, or call a subroutine. Later versions (for example, the PDP-14/30) are based on PDP-8 physical packaging technology. I/O is line voltage. ;
PDP-15: DEC's final 18-bit machine (1970). It is the only 18-bit machine constructed from
TTL integrated circuits rather than discrete transistors, and, like every DEC 18-bit system (except mandatory on the PDP-1, absent on the PDP-4) has an optional integrated
vector graphics terminal, DEC's first improvement on its early-designed 34n where n equalled the PDP's number. Later versions of the PDP-15 run a real-time multi-user OS called "XVM". The final model, the PDP-15/76 uses a small PDP-11 to allow Unichannel peripherals to be used. ;
PDP-16: A "roll-your-own" digital system using
Register Transfer Modules,{{cite web ==Related computers==