KDF9 was an early British 48-bit computer designed and built by English Electric (which in 1968 was merged into International Computers Limited (ICL)). The first machine came into service in 1964 and the last two of the 29 machines were decommissioned in 1980 at the National Physical Laboratory. The KDF8, developed in parallel, was aimed at commercial processing workloads.

The KDF9 was an early example of a machine that directly supported multiprogramming, using offsets into its core memory to separate the programs into distinct virtual address spaces. Several operating systems were developed for the platform, including some that provided fully interactive use through PDP-8 machines acting as smart terminal servers. A number of compilers were available, notably both checkout and globally optimizing compilers for Algol 60.

Architecture

The logic circuits of the KDF9 were entirely solid-state. The KDF9 used transformer-coupled diode–transistor logic, built from germanium diodes, about 20,000 transistors, and about 2,000 toroid pulse transformers. They ran on a 1 MHz clock that delivered two pulses of 250 ns separated by 500 ns, in each clock cycle. The maximum configuration incorporated 32K words of 48-bit core storage (192K bytes) with a cycle time of 6 microseconds. Each word could hold a single 48-bit integer or floating-point number, two 24-bit integer or floating-point numbers, six 8-bit instruction syllables, or eight 6-bit characters. at the University of Leeds, and COTAN, developed by UKAEA Culham Laboratories with the collaboration of Glasgow University, were fully interactive multi-access systems, with PDP-8 front ends to handle the terminals.

The Kidsgrove and Whetstone Algol 60 compilers were among the first of their class. The Kidsgrove compiler stressed optimization; the Whetstone compiler produced an interpretive object code aimed at debugging. It was by instrumenting the latter that Brian Wichmann obtained the statistics on program behaviour that led to the Whetstone benchmark for scientific computation, which inspired in turn the Dhrystone benchmark for non-numerical workloads.

Reminiscence

Machine code orders were written in a form of octal officially named syllabic octal

Notes

References

  • The English Electric KDF9
  • The Hardware of the KDF9
  • The Software of the KDF9
  • The KDF9 and Benchmarking
  • The KDF9: a Bibliography
  • The KDF9 character codes
  • ee9, a KDF9 emulator written in Ada 2012
  • paskal, a KDF9 Pascal cross compiler written in Ada 2012
  • Delivery List and applications for the English Electric KDF9
  • History of KDF9 Algol compiler
  • The Whetstone KDF9 Algol Translator
  • Some KDF9 Algol compiler anecdotes
  • Presentation on KDF9 Algol on visit from Dijkstra
  • KDF9 Nest (images)
  • Source Code for KDF9 port of Atlas Autocode compiler