| Developer | English Electric |
|---|---|
| Manufacturer | English Electric |
| Generation | 2 |
| Release date | 1964 |
| Units shipped | 29 |
| Operating system | Timesharing Director, Eldon 2, EGDON, COTAN |
| CPU | Transformer-coupled diode–transistor logic, built from germanium diodes, about 20,000 transistors, and about 2,000 toroid pulse transformers) @ 1 MHz |
| Memory | 32K words of 48-bit core storage (192K bytes) |
| Mass | 5.2 short tons (4.7 t) |
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 of 29 machines was decommissioned in 1980 at the National Physical Laboratory. The KDF9 was designed for, and used almost entirely in, the mathematical and scientific processing fields – in 1967, nine were in use in UK universities and technical colleges.[1] 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.