Elliott 803
Most sales were of the 803B version with more parallel paths internally, larger memory and hardware floating-point operations.
The Elliott 803 was the computer used in the ISI-609, the world's first process or industrial control system, wherein the 803 was a data logger.
[7] The central processing unit (CPU) is housed in one cabinet with a height, width, and depth, of 56 by 66 by 16 inches (142 by 168 by 41 cm).
The operator's console, about 60 inches long, allows low-level instructions to be entered manually to manipulate addresses and data and can start, stop and step the machine: there is a loudspeaker (pulsed by the top bit of the instruction register) which allows the operator to judge the status of a computation.
The system requires air conditioning, drawing about 3.5 kW of power in a minimal configuration.
[8] Optional mass storage is available on an unusual magnetic tape system based on standard 35 mm film stock coated with iron oxide (manufactured by Kodak).
Elliott's factory at Borehamwood was close to the Elstree film studios which explains the use of the 35mm sprocketed media.
Depending on their polarity, current pulses in the input windings either magnetise the core or cancel each other out.
Two clock phases designated alpha and beta are used to trigger (reset to zero) alternate cores.
Instructions and data are based on a 39-bit word length with binary representation in 2's complement arithmetic.
Although it is believed that the single length divide and square root instructions were only enabled in 803s destined for process control applications, the one remaining operational 803B has been found to have these instructions enabled, probably because it was used by a software house to develop real time and process control applications.
These 19-bit instructions are packed two to a word with an additional 39th bit between them, the so-called B-line or B digit (the term is a legacy from the Ferranti Mark 1 computer, where the A-line represented the accumulator and the B-line an instruction modifier, both stored on a Williams tube).
These are fixed point arithmetic with 4 different combinations of operand and result destination: Group 4 is conditional and unconditional jumps.
change the B-modified second half of location 1 from a 16 to a 17 instruction, which sets a to n - a instead of clearing it, as required by the inner loop.)
Interrupts are probably used mostly in conjunction with custom interfaces provided as part of ARCH real time process control systems.
Location 5 is expected to contain a standard subroutine entry instruction pair (73 LINK : 40 N – see above), allowing the pre-interrupt execution address (still in the SCR) to be saved for later return.
This has no formula translation facilities and requires all calculations to be reduced to a series of assignments with no more than a single operator on the right hand side.
Hoare recounts some of his experiences at Elliotts in his 1980 Association for Computing Machinery (ACM) Turing Award lecture.
[3] The most popular applications were in civil engineering and architecture, for structural analysis, cut and fill, survey correction, and bills of quantities.
