PDP-9
| Industry | Computer hardware |
|---|---|
| Founded | May 16, 1957 |
| Products | PDP-9 minicomputer |
The PDP-9 was the fourth model in a series of five 18-bit minicomputers produced by Digital Equipment Corporation, introduced in 1966. A total production run of 445 units was achieved, which included 40 units of the more affordable and compact PDP-9/L variant.
History
Positioned after the earlier 18-bit machines—the PDP-1, PDP-4, and PDP-7—the PDP-9 was eventually succeeded by the PDP-15.
Hardware
With dimensions approximately two meters in width and 75 centimeters in depth, the PDP-9 delivered nearly twice the processing speed compared to the PDP-7. Constructed using discrete transistor technology, it offered an optional integrated vector graphics terminal, a memory cycle time of 1 microsecond, and had an estimated weight of . The budget-friendly PDP-9/L model featured a slightly slower memory cycle time of 1.5 microseconds and weighed about .
Marking DEC's inaugural use of microprogramming, the PDP-9 supported peripherals such as a 300 cps paper tape reader, a 50 cps paper tape punch, DECtape drives for operating system and file storage, along with a Model 33 KSR console teleprinter operating at 10 cps.
Significant enhancements over the PDP-7 included:
- Introduction of status flags to detect errors in reader and punch devices
- Implementation of a multi-level interrupt mechanism known as Automatic Priority Interrupt (API)
- Improved memory management functionality
User-led innovations extended the PDP-9's capabilities by adding hardware support for floating-point arithmetic—a remarkable feature for its cost category—and enabled the creation of a parallel computing system controlled by the PDP-9.
Software
The PDP-9 ran ADSS (ADvanced Software System), a single-user keyboard monitor operating system. For development purposes, DECsys provided an interactive environment supporting both Fortran and assembly language programming.
Versions of FORTRAN II and FORTRAN IV were available on this platform.
MUMPS, initially developed on the PDP-7, was also executed on multiple PDP-9 systems at Massachusetts General Hospital.
Sales
While the PDP-7 achieved sales of 120 units and was regarded as "highly successful," the PDP-9 saw greater distribution with 445 units sold. Although variants such as the PDP-7A and PDP-9/L were produced, these submodels did not substantially influence total sales figures.
See also
- Programmed Data Processor
- PDP-15 - the direct successor to the PDP-9