at 100 cards per minute. The DEUCE Mark IIA provided seven extra mercury delay lines, each of 32 words. A total of 33 DEUCE machines were sold between 1955 and 1964, two being purchased by the engine manufacturer Bristol Siddeley. The success of DEUCE was due to its program library of over 1000 programs and subroutines. Hardware characteristics DEUCE Mark 0 and I: Clock rate 1 MHz Word size 32 bits High speed store 384 words Arithmetic: one 32-bit accumulator; one 64-bit accumulator that could be used also as two 32-bit accumulators. addition/subtraction 64 microseconds single length, 96 microseconds double precision Addition of a single-length number to a double-length number, with automatic sign extension, 64 microseconds. multiplication 2080 microseconds division 2112 microseconds magnetic drum 8192 words separate read heads and write heads Track read time 15 ms Head shift time 35 ms card reader speed 200 cards per minute card punch speed 100 cards per minute paper tape reader speed 850 character/second tape: 5, 7, 8-row tape. stopping time: ½ millisecond (m.s.) start time 20 milliseconds paper tape punch speed 25 characters/second tape: 5 or 7 rows Software floating-point (average times): addition/subtraction 6 m.s. multiplication 5½ m.s. division 4½ m.s. DEUCE MARK II: As for DEUCE Mark I. A combined IBM 528 card reader and punch could read cards at 200 per minute, and punch at 100 cards per minute. When simultaneously started, the reader and punch ran at 100 cards per minute. Automatic conversion to and from 6-bit characters was provided. This mode was in addition to the programmed conversion provided by the Mark I DEUCE. DEUCE MARK IA AND IIA: As above, with 7 extra delay lines providing 224 words of high-speed store. Notes: The multiplier and divider were asynchronous. Several integers could be multiplied in a single execution of the multiply instruction, by inserting integers in the multiplier or multiplicand registers during multiplication, and by extracting results during multiplication. Other special effects included counting the bits in a word, and converting Binary Coded Decimal (BCD) to binary. Similarly for division, which could be used for converting integers to Binary Coded Decimal (BCD), and for converting pounds, shillings, and pence to pence. See also List of vacuum tube computers References External links This site has an extensive collection of original documents, including programs, subroutines, DEUCE News, and bulletins. Oral history interview with Donald W. Davies, Charles Babbage Institute,