was an early British computer designed and built by English Electric
, later English Electric Leo Marconi, EELM, later still incorporated into ICL
. It first came into service in 1964 and was still in use in 1980 in at least one installation. The present article presents a synoptic overview of the architecture of the KDF9; for a more complete account, see ‘The English Electric KDF9’, and ‘The Hardware of the KDF9’, at the links below.
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 two-phase clock. 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 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. There was also provision for efficient handling of double-word, 96-bit, numbers in both integer and floating point formats. However, there was no facility for byte or character addressing, so that non-numerical work suffered by comparison. Moreover, there was no standard character set. Each I/O device type had its own more or less similar character code. Not every character that could be read from paper tape could be successfully printed, for... Read More