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32-bit pointers, known as PAS (Paged
Address Space) addressing. Each process has a PAST (Program Accessible Segment Table) which lists which of the system's memory segments the program is permitted to access. CST addressing allows four of the PAST entries to be mapped at addresses 0, 16KiB, 32KiB, and 48KiB, giving the 16-bit/64KiB address space. Programs which use more than 64KiB of memory must explicitly map the PAST entries they require at any moment into their 4 CST entries, although Nucleus will automatically map different code segments into the CSTs. PAS addressing allows programs to view their address space as a flat 32-bit address space, with successive PAST entries appearing every 16KiB, and Nucleus performing the PAST entry segment mapping automatically. The 32-bit systems support mixing of CST and PAS addressing in the same process. All instructions are 16 bits wide, except for some PAS addressing instructions which are 32 bits. Instructions can only be run from CST address space.
368:
into the
Nucleus firmware, and thus I/O operations on the IMC did have some impact on CPU performance, although the 4x6x systems could have external IOPs added. The 4000 series Nucleus I/O instructions and system tables allow for up to 8 IOPs, although most of the models in the 4000 series range had some type of hardware limitation which reduced this. The 408x systems had 4-ported store, with the CPU and first IOP sharing one of these, and up to three additional IOPs connected to the remaining store ports. (Early documentation shows these additional store ports were also designed to connect additional CPUs, although this was not a configuration which was ever sold using 4080 processors.) Later models had more store ports, depending on how many store port boards could be fitted into the system. The 4190 could support the full complement of eight IOPs, and the 4190D supported eight IOPs with two CPUs.
863://****************************************************************************** ROUTINE FACT(VALUE) // return factorial of RA. VALUE => RESULT WHILE DECREMENT VALUE GT //0// DO << RESULT * VALUE => RESULT >> RETURN(RESULT) END //****************************************************************************** ENTRYPOINT: OPEN(TO, 1) // Print factorials for numbers 1 through 9 1 => RA REPEAT << RA => COUNT FACT(RA) => RA TOCHAR(RA, 7, ANSWER + 13) TOCHAR(COUNT, 2, ANSWER + 9) PUT(TO, 20, ANSWER) COUNT + 1 => RA >> WHILE RA LT 10 CLOSE(TO) STOP(0) END //******************************************************************************
364:. The I/O controllers on each IOP would each occupy one or more Ways, depending on how many simultaneous I/O operations they need to handle. The IOP polices each Way's access to main store, allowing only access to successive memory locations defined for the I/O operation that Way is currently performing. The earlier IOPs performed 8-bit and 16-bit wide store accesses, with a burst mode for doing up to 8 transfers together for higher throughput I/O controllers. The later IOPs added 32-bit wide store accesses.
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segments, processes which can change the routing of messages between other processes or change the mapping of I/O devices to processes, etc. Normally system table access is limited to relatively few trusted processes, and other processes which need to perform operations such as loading processes, allocating memory, etc. will pass a message to the relevant trusted process which it will vet before performing the action and replying.
305:
registers are used as 16-bit pointers. A 16-bit L register points to function local data, and a G register always contains zero which can be used as a 16-bit global pointer, and also an 8-bit, 16-bit, or 32-bit zero value. The 16-bit S (sequence) register points to the next instruction to be obeyed. The 8-bit EC register contains condition codes bits. (Some of this is illustrated in the much simpler instruction set of the
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30:
335:. In Basic Test mode, Nucleus is disabled, I/O is performed differently, and only a single program can run, restricted to the bottom 64KiB of store, but all other non-nucleus and non-PAS instructions operate normally. This mode is used very early during booting to set up the system tables required by Nucleus, before obeying a
309:.) A read-only 'keys' register allows programs to read the value set on the front panel toggle switches by the operations staff. No 32-bit PAS pointer register exists—32-bit PAS pointers reside in memory in the 16-bit CST address space, and are accessed by using a 16-bit pointer. There is no instruction set support for a
137:
8-bit minicomputer. Beta followed and became the GEC 4080. Gamma was never developed, so a few of its enhanced features were consequently pulled back into the 4080. The principal designer of the GEC 4080 was Dr. Michael
Melliar-Smith and the principal designer of the 4060 and 4090 was Peter Mackley.
432:
All the IOPs designed and built through the 1970s provided the same Normal
Interface bus for I/O Controllers, and the I/O controllers could generally be used in any of them. In the 1980s, some more specialised IOPs were designed. A Direct Memory Access Director (DMAD) IOP allowed for a new type of
367:
All systems have at least one IOP. On the 4080, this first IOP was called the Basic
Multiplexer Channel, or BMC, and the 4080 front panel provides for controlling both the CPU and the BMC. The entry level 415x and 4x6x systems have their first IOP (Integral Multiplexer Channel, or IMC) integrated
316:
The instruction set contains instructions which operate register-register, store-register, register-store, and store-store. There are a set of string manipulation instructions which operate on variable lengths of store, copying, comparing, or scanning for a pattern. There are a number of
Nucleus
304:
The 32-bit A register is the main accumulator register. There is a 32-bit B register too, which is most commonly used together with the A register as a 64-bit BA register for double-precision floating point operations. A 16-bit X register is used mainly for array indexing, and two 16-bit Y and Z
300:
The model numbers below 4090 are 16-bit processors, and model numbers from 4090 upwards are mixed 16-bit and 32-bit. This relates to pointer sizes available to programs. All systems support 16-bit pointers, which is known as CST (Current
Segment Table) addressing. The 32-bit systems also support
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Nucleus is configured by a set of system tables, and processes which have a need to modify the operation of nucleus are given access to the relevant system tables. This would be the case for processes which directly change the state of other processes, processes which allocate and delete memory
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crate controller was also available (again, used for process control interfacing). The Normal
Interface bus which these controllers plug into is a published interface, and many customers also built their own controllers for their own specific process control requirements. The earlier GEC 2050
195:, and consequently operating systems running on GEC 4000 series systems do not need to directly provide these features themselves. Nucleus firmware cannot be reprogrammed by any code running on the system, and this made the systems particularly attractive to a number of security applications.
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instruction. Once the system has switched to Full
Nucleus, it cannot return to Basic Test mode without operator intervention at the front panel, in effect killing any operating system which was running. Basic Test mode is also used to run certain test software (hence the name).
862:
PROCESS CHAPTER FACTORIAL ENTRY LABEL ENTRYPOINT LITERAL TO = 4 // Assume using the default proforma EXTERNAL ROUTINE OPEN, PUT, CLOSE, TOCHAR VECTOR OF BYTE ANSWER = "factorial x = xxxxxx" HALF COUNT HALF VALUE FULL RESULT
437:
IOP generated a SCSI bus for attaching more modern disks, and also included an integrated
Interval Timer, system console controller, and Calendar Clock so that an additional Normal Interface IOP and separate controllers was not required to support just these functions.
250:
code, and other features which are often found within operating system kernels must be run in processes on the 4000 systems. Inherent in this is that they are all running in their own address spaces, protected from the actions of each other, just as all processes are.
356:, each of which interfaces between the store and a set of I/O controllers. The IOPs are controlled by the Nucleus function in the CPU, but once an I/O event is triggered, they operate autonomously without interaction with the CPU until the I/O completes. The
313:. There are a number of registers inaccessible to programs which are used by Nucleus, such as the hardware segment registers which point to the running process's four CSTs, master segment and PAS segments, and the system tables.
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instructions for tasks such as sending a message to another process or a peripheral device, receiving a message or interrupt, changing a CST entry to point to a different segment which is accessible to the process, etc.
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controllers (using between 4 and 32 Ways). A digital I/O board (using four Ways) was commonly used for direct process control interfacing, and for providing a fast parallel link between systems. A
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the ageing Elliott 900 series, and needed to develop a new range of systems. Three ranges were identified, known internally as Alpha, Beta, and Gamma. Alpha appeared first and became the
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used GEC 4080 processors at three of their Grid Control Centres. Known as GI74, they were used to collect data from substations and display this on the wall diagrams and tabular VDUs.
160:
factory and development returned to Borehamwood. The last systems were manufactured around 1995. There were still a few GEC 4220 systems operating in 2018 with maintenance provided by
324:. This becomes a four-stage pipeline for the 4220, the highest-performing system in the series. The entry-level 415x and 4x6x systems have only a single-stage pipeline.
153:
for the development of the 4000 series, particularly Nucleus. By 1991, the number of systems manufactured was falling off, so manufacture was transferred to
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There is no provision for running any supervisor/privileged/kernel mode code on the 4000 systems—all operating system code runs as processes. Hence,
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Users of GEC 4000 series systems included many British university physics and engineering departments, the central computing service of
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I/O controller which had more freedom to access main memory, and allowed the design of more intelligent communications controllers. A
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minicomputer used an 8-bit version of the Normal Interface, and most I/O Controllers could be used on both ranges of systems.
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At the Rutherford-Appleton Laboratory a GEC 4000 system was used to control the synchrotron and injectors used for the
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offices in Elstree Way. Development and manufacture transferred to the company's new factories in Woodside Estate,
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P. J. Denning, "ACM president's letter: computer architecture: some old ideas that haven't quite made it yet",
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and Durham Fire Brigade for command and control systems. The computers controlled most of the world's national
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A number of variants of the GEC 4000 processor were produced, including (in approximate chronological order):
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1172:. Ellis Horwood Series In Computers And Their Applications (1 ed.). Chicester, West Sussex, UK:
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bus interface) disk controllers for controlling up to four drives (all using two Ways),
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IOPs can each support up to 255 or 256 simultaneous I/O operations, each on a separate
188:. Nucleus implements a number of features which are more usually implemented within an
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A GEC 4080M was used as the central processor for the radar system of the ill-fated
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The 4000 series systems were developed and manufactured in the UK at GEC Computers'
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690:: cheaper, slower version of the 4195 (no memory cache, no fast multiply unit)
654:: cheaper, slower version of the 4190 (no memory cache, no fast multiply unit)
25:
GEC 4000 series computers at GEC Computers' Dunstable Development Centre, 1991
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Several operating systems were available for the GEC 4000 series, including:
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642:: Am2900-based with 32-bit addressing extensions and up to 4 MiB of memory
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system supporting batch and interactive use, and transaction processing
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94: in this section. Unsourced material may be challenged and removed.
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678:: 4160 with DMAD IOP(s) for high speed communications controllers
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in the United Kingdom during the 1970s, 1980s and early 1990s.
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331:. All systems also support a limited mode of operation called
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764:: Disk Operating System, for real-time systems, providing a
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in the late 1970s. In 1979, GEC Computers was awarded the
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used them for real-time control of rolling steel mills,
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controller (all these use a single Way), a number of
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1131:
994:"Central Processor Unit Instruction Set (GEC 4080)"
660:: compact ruggedised 4060 for military applications
636:: compact ruggedised 4080 for military applications
1236:The Centre for Computing History – Computer Museum
1163:Salomon, David (February 1993). "6.1.4 BABBAGE".
666:: 4065 with the 4090 32-bit addressing extensions
1728:
1142:(2nd ed.). Oxford: Market House Books Ltd.
1128:
1052:"User Hardware Handbook – Interfaces (GEC 4080)"
928:"Press Release: GEC Computers wins Queens Award"
899:"Central Processor Unit Controls and Monitoring"
348:The 4000 I/O design is based around a number of
594:: entry-level model without memory interleaving
327:The normal operating mode of the CPU is called
164:, and some GEC 4310 were operating until 2013.
1679:GEC-Marconi scientist deaths conspiracy theory
716:IOP replacing the default Normal Interface IOP
1257:
125:was formed in 1968 as a business unit of the
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413:" tape drives, and a number of multi-ported
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371:Some commonly used I/O Controllers are the
168:continues to use GEC 4190 systems in 2022.
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839:. It appeared in 1971. It was named after
1138:Illingworth, V. (1986). "B.001 Babbage".
795:Programming languages available included
579:: original 1973 model with 64–256 KiB of
110:Learn how and when to remove this message
1762:Computers designed in the United Kingdom
1178:Simon & Schuster International Group
184:included a pioneering facility known as
28:
20:
1162:
952:"Central Processor Unit Nucleus Manual"
648:: revised 4090 with up to 16 MiB memory
291:base-16 excess-64 floating point format
151:Queen's Award for Technical Achievement
1729:
755:: Core Operating System, for diskless
234:directly by processes, and routing of
1245:
1709:
1339:Vickers Shipbuilding and Engineering
630:: 4060 supporting up to 1 MiB memory
562:Central Electricity Generating Board
92:adding citations to reliable sources
63:
13:
1618:South African Class 10E1, Series 2
1613:South African Class 10E1, Series 1
1197:from the original on 23 March 2020
1023:"C.P.U. Basic Multiplexer Channel"
739:-based system emulating a GEC 4220
258:
225:memory segmentation and protection
14:
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1747:Computers using bit-slice designs
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588:: 4080 with up to 1 MiB of memory
16:Series of 16/32-bit minicomputers
1708:
1697:
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1608:South African Class 9E, Series 2
1603:South African Class 9E, Series 1
1398:Associated Electrical Industries
1085:Engineering Computing Newsletter
522:for real-time train scheduling,
129:conglomerate. It inherited from
68:
1461:Robert Stephenson and Hawthorns
1081:"The last of the British minis"
933:. 21 April 1979. Archived from
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79:needs additional citations for
1365:GEC Plessey Telecommunications
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1073:
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1015:
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973:
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547:spallation source until 1998.
464:Rutherford-Appleton Laboratory
383:reader and punch controllers,
1:
1488:Radio & Allied Industries
884:
610:: entry-level model based on
833:high level assembly language
801:high-level assembly language
441:
7:
1223:25 years of GEC 4000 series
1061:. April 1977. pp. 4–25
866:
784:: Secure Operating System (
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403:controllers for up to four
10:
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1314:Marconi Electronic Systems
850:
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458:academic/research network
171:
59:
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1593:GEC Stephenson locomotive
1580:
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1429:Siemens Brothers & Co
1383:
1347:
1279:
1229:"GEC and the 4000 Series"
983:, 24 (9), 1981, page 553.
981:Communications of the ACM
859:for numbers from 1 to 9.
722:: Reimplement 4190 using
567:
508:British Steel Corporation
448:University College London
320:The 4080 has a two-stage
1273:General Electric Company
835:for the GEC 4000 series
158:Beeston, Nottinghamshire
1408:British Thomson-Houston
1329:Marconi Research Centre
1140:Dictionary of computing
768:and swapping facilities
530:systems, including the
350:Input/Output Processors
1598:South African Class 4E
1524:Marconi Communications
1476:Willans & Robinson
1355:Alenia Marconi Systems
1166:Assemblers and Loaders
555:airborne early warning
263:The 4000 series has a
34:
26:
1588:British Rail Class 91
1434:William Thomas Henley
1375:Thomson Marconi Sonar
1348:Former joint ventures
1304:Hirst Research Centre
1234:"GEC 4000 Computer",
1174:Ellis Horwood Limited
855:This code prints the
706:: dual-processor 4190
32:
24:
1483:Gilbarco Veeder-Root
1466:Ruston & Hornsby
1446:Dick, Kerr & Co.
1424:Metropolitan-Vickers
1180:. pp. 184–185.
726:processor technology
468:Daresbury Laboratory
462:switching backbone,
422:serial communication
322:instruction pipeline
176:The GEC 4000 series
88:improve this article
33:GEC 4080 front panel
1503:Yarrow Shipbuilders
1370:Matra Marconi Space
1324:Marconi-Osram Valve
1319:Marconi Instruments
1280:Former subsidiaries
940:on 22 October 2019.
847:computing pioneer.
790:multilevel security
524:London Fire Brigade
337:Switch Full Nucleus
1106:"BAe Nimrod AEW 3"
880:8-bit minicomputer
520:London Underground
472:Harwell Laboratory
198:Nucleus performs:
166:London Underground
131:Elliott Automation
35:
27:
1724:
1723:
1626:
1625:
1393:A.B. Dick Company
1209:(xiv+294+4 pages)
1059:GEC 4000 Computer
1030:GEC 4000 Computer
1001:GEC 4000 Computer
959:GEC 4000 Computer
906:GEC 4000 Computer
757:real-time systems
238:back to processes
209:context switching
120:
119:
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54:GEC Computers Ltd
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1757:32-bit computers
1752:16-bit computers
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1663:Arnold Weinstock
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1451:Elliott Brothers
1441:English Electric
1386:and acquisitions
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1112:. Archived from
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358:Normal Interface
289:arithmetic, and
287:two's complement
190:operating system
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1456:Marconi Company
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1032:. December 1977
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1003:. December 1977
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961:. December 1977
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908:. December 1977
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841:Charles Babbage
831:Babbage is the
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492:British Telecom
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268:instruction set
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259:Instruction set
221:message passing
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684:: compact 4190
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74:
67:
61:
58:
15:
9:
6:
4:
3:
2:
1774:
1763:
1760:
1758:
1755:
1753:
1750:
1748:
1745:
1743:
1742:GEC Computers
1740:
1738:
1737:Minicomputers
1735:
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1567:GEC Series 63
1565:
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1289:GEC Computers
1287:
1286:
1284:
1282:and divisions
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1187:0-13-052564-2
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1168:
1167:
1159:
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1149:0-19-853913-4
1145:
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1116:on 2 May 2012
1115:
1111:
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923:
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890:
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873:GEC Series 63
871:
870:
860:
858:
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837:minicomputers
834:
824:
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629:
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619:
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602:semiconductor
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450:(Euclid) and
449:
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420:
416:
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401:magnetic tape
398:
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391:(and earlier
390:
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219:asynchronous
218:
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169:
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132:
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123:GEC Computers
114:
111:
103:
100:February 2022
93:
89:
83:
82:
77:This section
75:
71:
66:
65:
57:
55:
51:
50:minicomputers
48:
44:
40:
31:
23:
19:
1714:
1702:
1638:Cyril Hilsum
1561:
1384:Predecessors
1299:GEC Traction
1294:GEC Research
1235:
1199:. Retrieved
1165:
1158:
1139:
1118:. Retrieved
1114:the original
1109:
1100:
1088:. Retrieved
1084:
1075:
1063:. Retrieved
1058:
1046:
1034:. Retrieved
1029:
1017:
1005:. Retrieved
1000:
988:
980:
975:
963:. Retrieved
958:
946:
935:the original
922:
910:. Retrieved
905:
893:
854:
830:
794:
781:
761:
752:
747:
729:
719:
712:: 4195 with
709:
703:
693:
687:
681:
675:
669:
663:
657:
651:
645:
639:
633:
627:
623:
607:
600:: 4082 with
597:
591:
585:
576:
571:
559:
552:Nimrod AEW.3
549:
539:
516:British Rail
445:
431:
419:asynchronous
385:line printer
381:punched tape
379:controller,
370:
366:
361:
357:
353:
347:
344:Input/output
336:
332:
329:Full Nucleus
328:
326:
319:
315:
303:
299:
262:
253:
241:
197:
185:
175:
140:
121:
106:
97:
86:Please help
81:verification
78:
52:produced by
38:
36:
18:
1581:Locomotives
1519:BAE Systems
1414:Edison Swan
1360:GEC Alsthom
581:core memory
415:synchronous
283:addressable
248:file system
143:Borehamwood
1731:Categories
1643:Hugo Hirst
1512:Successors
1225:(archived)
885:References
805:FORTRAN IV
776:multi-user
766:filesystem
724:gate array
620:processors
557:aircraft.
480:Met Office
333:Basic Test
279:big-endian
236:interrupts
215:semaphores
213:efficient
205:scheduling
1550:Computers
1201:1 October
1090:7 January
857:factorial
786:DOD A1/B3
698:rackmount
618:bit-slice
537:service.
512:BHP Steel
498:(Italian
442:Customers
352:known as
293:(same as
270:. It has
147:Dunstable
1703:Category
1557:GEC 2050
1543:Products
1419:Hotpoint
1192:Archived
878:GEC 2050
867:See also
809:CORAL 66
744:Software
535:viewdata
528:Videotex
307:GEC 2050
285:memory,
182:firmware
178:hardware
135:GEC 2050
39:GEC 4000
1715:Commons
1065:15 June
1036:15 June
1007:15 June
965:15 June
912:15 June
851:Example
845:English
827:Babbage
797:Babbage
737:MVME187
545:neutron
532:Prestel
504:Plessey
502:), and
408:⁄
281:, byte-
203:process
186:Nucleus
172:Nucleus
60:History
1631:People
1572:OS4000
1529:Telent
1493:Tracor
1403:Birlec
1184:
1146:
1120:17 May
772:OS4000
615:Am2900
604:memory
568:Models
454:, the
397:Pertec
193:kernel
162:Telent
47:32-bit
1672:Other
1534:Unify
1410:(BTH)
1334:Osram
1195:(PDF)
1170:(PDF)
1055:(PDF)
1026:(PDF)
997:(PDF)
955:(PDF)
938:(PDF)
931:(PDF)
902:(PDF)
843:, an
821:BASIC
813:ALGOL
782:SCP-2
704:4190D
658:4060M
634:4080M
500:telco
456:JANET
426:CAMAC
311:stack
275:bytes
272:8-bit
155:GPT's
1203:2008
1182:ISBN
1144:ISBN
1122:2009
1092:2017
1067:2009
1038:2009
1009:2009
967:2009
914:2009
819:and
774:: a
730:4310
720:4220
714:SCSI
710:4193
700:4150
694:4151
688:4185
682:4195
676:4162
670:4150
664:4160
652:4180
646:4190
640:4090
628:4065
624:4062
608:4060
598:4085
592:4070
586:4082
577:4080
560:The
542:ISIS
518:and
510:and
484:CERN
476:NERC
460:X.25
435:SCSI
417:and
399:PPC
393:disk
354:IOPs
265:CISC
180:and
37:The
817:APL
803:),
799:(a
762:DOS
753:COS
612:AMD
496:SIP
488:ICI
389:SMD
362:Way
297:).
232:I/O
127:GEC
90:by
1733::
1190:.
1176:/
1130:^
1108:.
1083:.
1057:.
1028:.
999:.
957:.
904:.
823:.
815:,
811:,
807:,
788:)
732::
696::
506:.
494:,
490:,
486:,
482:,
478:,
474:,
470:,
466:,
375:,
277:,
246:,
43:16
1265:e
1258:t
1251:v
1205:.
1152:.
1124:.
1094:.
1069:.
1040:.
1011:.
969:.
916:.
626:/
410:2
406:1
113:)
107:(
102:)
98:(
84:.
45:/
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
