GEC 4080 Computer
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It was in 1968 that the real-time computing interests of AEI, Elliott-Automation, English Electric and Marconi together with those of GEC, were consolidated under Government inspiration into a single company. It traded initially as Marconi Elliott Computer Systems Ltd until registration in its present name of GEC Computers Ltd could be completed.
The company was set up as a design and manufacturing centre for the multi-faceted GEC group, as well as an independent computer supplier. Today it employs more than 900 staff and with orders worth £22 million for this year, more expansion at its new manufacturing plant in Dunstable seems inevitable
The strengths of the 4OOO series lie particularly in its operating system and related features. OS4000 is a multiprogramming, multi-access operating system supporting a segmented virtual memory; the important scheduling and address-mapping functions are provided by a nucleus which is implemented in fast-access firmware - GEC was among the pioneers of this technique. This method provides the following advantages.
Up to 256 active schedulable processes. A single process may have up to 255 segments where a. segment is 16KNB and no more than four are currently in memory.
The GEC 4080 is specifically designed to provide a major advance in the rapidly developing medium to large-scale automation system field. It comprises a range of basic units providing central processor, store and input/output facilities extending over a wide range of system size; other processors may be added to provide major standard or special input/output extensions, or to extend the general purpose processing capability of the system.
The minimum configuration contains one module of store (either 32 or 64 kilobytes) and one central processor with its built-in input-output multiplexer capable of accommodating up to 256 fully autonomous peripheral devices. Control teleprinter and paper tape equipment are also required. This configuration will occupy a standard 6ft. rack with room to spare.
Larger configurations may contain up to 256 kilobytes of store, magnetic discs, line printer, magnetic tape, communications peripherals, etc.
The Central Processor of 4080 provides extensive logical, integer and floating point manipulation facilities in a high speed multiple register hardware system. Data formats provided are:-
Byte: 8 bits
Half-Word: 16 bits
Fullword: 32 bits
Floating Point: 24 bits fraction, 7 bits exponent
Floating Point: 56 bits fraction, 7 bits exponent
Modern, MSI hardware techniques enable 4080 to provide directly interpreted hardware instructions operating on all these formats.
Index registers and special address mapping logic also result in fast and extremely flexible address structuring. There are five formats for store reference, including three specifically designed for accessing arrays of varying complexity, as well as formats for register to register, literal and branch instructions.
These features result in a processor which is not only fast by any standards, but also which can save considerable amounts of time and store-space by performing in one operation tasks that would take other computers many instructions. For instance, 4080 may scan through an array of characters packed in store until any of a number of pre-specified characters are found - in one instruction!
And to ensure that maximum advantage is obtained from all resources in the system, store accesses are interleved to optimise store utilisation.
The control in the picture is a dual computer control for computers A and B. We understand that as it was controlling a strip mill in Sheffield if one computer failed it could be immediately switched to the second one
We also have other accessories and modules which are not shown
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This exhibit has a reference ID of CH3894. Please quote this reference ID in any communication with the Centre for Computing History.