Programmed Data Processor
| Company type | Product line |
|---|---|
| Industry | Computer hardware |
| Founded | 1957 |
| Founder | Digital Equipment Corporation |
| Defunct | 1990 |
| Products | Minicomputers (PDP-1, PDP-4, PDP-5, PDP-6, PDP-7, PDP-8, PDP-9, PDP-10, PDP-11, PDP-12, PDP-14, PDP-15, PDP-16) |
| Parent | Digital Equipment Corporation |
Programmed Data Processor (PDP), occasionally referred to as "Programmable Data Processor," was a designation used by Digital Equipment Corporation between 1957 and 1990 for various minicomputer product lines.
The term "PDP" was intentionally chosen to exclude the word "computer" because computers at that time were viewed as large, intricate, and expensive machines. Early investors were resistant to Digital's efforts to develop a "computer," and the phrase "minicomputer" had yet to gain acceptance. Consequently, Digital repurposed its existing logic modules to produce a Programmed Data Processor aimed at customers unable to afford larger computing systems.
PDP models are typically categorized according to their word length.
Series
Prominent PDP models include:
- PDP-1
- The initial 18-bit system comprising four racks, instrumental in early time-sharing environments and influential within MIT’s hacker community. It fostered developments such as the first video game, Spacewar!, and early word processing applications. Partly derived from the TX-0, it utilized DEC’s existing modules. Production ended in 1969, with nearly all units still operational by 1975. The average system cost was approximately $120,000, significantly lower than competing computers of the period.
- Subsequent related models were the PDP-4, PDP-7, PDP-9, and PDP-15.
- PDP-3
- A distinctive 36-bit computer created in 1960 for the CIA’s Scientific Engineering Institute specifically for radar data processing; it was not offered commercially by DEC.
- PDP-4
- An 18-bit model introduced in 1962 featuring slower memory and different packaging compared to the PDP-1 but priced at $65,000. Around 54 units were sold. Later 18-bit systems (7, 9, 15) extended its instruction set. Noteworthy clients included Atomic Energy of Canada for reactor instrumentation.
- PDP-5
- DEC’s first commercially produced minicomputer and initial 12-bit model (1963). Its instruction set was expanded upon in the PDP-8. Over 1,000 units were manufactured.
- PDP-6
- The company’s first large-scale 36-bit system (1964), introducing its inaugural supported timesharing operating system. Only 23 installations occurred. Although it fell short of management expectations, it established the instruction set later used by the more successful PDP-10 and DECSYSTEM-20, which sold in the hundreds.
- PDP-7
- Released in 1964 as a successor to the PDP-4; this was DEC’s first wire-wrap system employing Flip-Chip modules. Approximately 120 units were sold. Bell Labs developed the initial versions of Unix and its predecessor language B on this platform.
- PDP-8
- A 12-bit computer launched in 1965 with a simplified instruction set; it became DEC’s first major commercial triumph and helped ignite the minicomputer revolution. More than 50,000 units were sold across multiple variants (A, E, F, I, S, L, M). Later models powered devices such as the DECmate word processor and VT-78 workstation.
- LINC-8
- Combined a PDP-8 CPU with a LINC CPU (1966), serving as a precursor to the PDP-12.
- PDP-9
- Successor to the PDP-7 and DEC’s first microprogrammed system (1966), delivering twice the speed of its predecessor. It featured a keyboard monitor interface with DIGITAL’s DECtape magnetic tape drives.
- PDP-10
- Also known as DECsystem-10, this popular 36-bit timesharing computer (1966) had several versions and models. Its instruction set evolved from that of the PDP-6. Variants like KL supported DECSYSTEM-20; KS targeted distributed computing as an affordable mainframe alternative.
- PDP-11
- Introduced in 1970 as a 16-bit machine and another commercial success lasting over twenty years with numerous implementations. The LSI-11 variant was primarily employed in embedded systems. The architecture influenced processors such as Motorola’s 68000 and Texas Instruments’ MSP430. Early VAX systems maintained backward compatibility with PDP-11 instructions.
- PDP-12
- A 12-bit machine from 1969 that merged features of LINC and PDP-8 architectures with selectable CPU modes. Later marketed under the name "Lab-8."
- PDP-14
- A controller designed for programmable logic control without data memory or registers (1969), intended for industrial use with Boolean logic commands.
- PDP-15
- DEC’s last 18-bit computer (1970), constructed from TTL integrated circuits instead of discrete transistors. It offered an optional integrated vector graphics terminal and supported a real-time multi-user operating system called "XVM." The final model incorporated a small PDP-11 CPU for peripheral compatibility.
- PDP-16
- A modular digital platform based on Register Transfer Modules aimed at industrial control tasks requiring capabilities beyond those of the PDP-14. The preassembled PDP-16/M ("Subminicomputer") debuted in 1972 and could be programmed for custom control or computational functions.
Related computers
- The TX-0, developed by MIT's Lincoln Laboratory, played a significant role in shaping DEC's product line, notably influencing Ben Gurley's PDP-1 design. After its memory was reduced and the instruction set enlarged, the system was transferred to MIT, where it operated alongside a PDP-1. This arrangement facilitated software migration and communication between the two machines.
- The LINC (Laboratory Instrument Computer), also originating from MIT's Lincoln Laboratory and partially constructed by DEC, acted as a direct predecessor to the PDP-12. Both the LINC and PDP-8 are recognized as pioneering minicomputers and early ancestors of personal computing devices. Among the PDP series, the PDP-8 and PDP-11 stand out as the most widely used models. Notably, Digital never officially released a PDP-20; however, the name was occasionally informally attributed to a PDP-10 running TOPS-20 (formally known as a DECSYSTEM-20).
- A number of unauthorized clones of the PDP-11 exist.
- Systems compatible with these architectures include models such as TOAD-1, TOAD-2, Foonly, and various Systems Concepts implementations of PDP-10/DECSYSTEM-20 machines.
References
- C. Gordon Bell, J. Craig Mudge, John E. McNamara, Computer Engineering: A DEC View of Hardware Systems Design (Digital, 1978)
- The Computer Museum Report, Volume 8: TX-0 alumni reunion, Spring 1984
- Bell, C.G., Grason, J., and Newell, A., Designing Computers and Digital Systems. Digital Press, Maynard, Mass., 1972.
- Interviews with David M. Razler, who owns and restores multiple PDP models.
External links
- Mark Crispin’s 1986 compilation of PDP models
- Operational examples of several PDP and LAB systems at a German computing museum
- Gordon Bell’s interview discussing DEC's PDP-6 as the inaugural commercial time-sharing computer at the Smithsonian Institution
- Timeline of DEC products
- Overview and application of Register Transfer Modules on Gordon Bell’s Microsoft webpage
- Recently refurbished PDP-12 featured at pdp12.lofty.com
- Comprehensive information on the PDP-7 and PDP7A including manuals and customer lists covering most units shipped
- Preliminary specifications for the Programmed Data Processor Model Three
- Catalog of PDP-related video games
Extensive documentation exists on Charles Lasner’s contributions and discussions on alt.sys.pdp8, offering in-depth knowledge about the PDP-8 family and associated DEC systems.