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GEC 4000 family
May 1979
Which Computer?
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.
GEC Computers has a good reputation for providing reliable real-time and process control computers especially for military environments and for use by other companies in the group. The 2050, an 8-bit machine, has been used widely in the real-time and communications market since its introduction in 1972. It is used in the public sector, including the Post Office, especially for remote job entry to a mainframe. There are also a few customers fro the SRS version, a stand-alone seat reservations system promoted among football clubs - user include Manchester United and Fulham.
The arrival of the more powerful 16-bit 4000 series is 1973 gave GEC Computers a basis for a much wider attack on the market. The opportunity to build on the 4000 series was helped by two important factors - public sector bodies, such as the Post Office and universities, are directed to buy British; and it had a ready made market within the GEC group, whose members are encouraged, although not compelled, to buy from GEC Computers.
GEC Computers traditionally has strong links with the university market, providing front-end computers for the ICL 1900as well as stand-alone machines. More recently its involvement with the EPSS packet-switching system and Prestel have involved a number of Post Office contracts for 4000s. the order book for 4000s stands at 260 systems with 200 installed.
GEC COMPUTERS provides a range of software-compatible 16-bit minicomputers. The low end of the family consists of the three machines, the 4060, 4062 and 4065, all of which may be mounted in a desk-style unit. They vary only in the type and capacity of storage available, and are the latest additions to the 4000 range. The 4062 can have a mixture of core and semiconductor store up to one megabyte; the other two machines use semiconductor memory, with the 4060 having a maximum of 256KB and the 4065 having an upper limit of 1MB.
GEC has been slow to introduce semiconductor memory. Two years ago it was the norm on U.S. minis, offering cost savings and lower power and cooling requirement than the older technology of ferrite cores.
More reliable
With the new semiconductor-based machines GEC has taken the architecture of its larger and more expensive 4070/4080 minis and implemented it with more LSI circuitry and lower internal speeds to produce a reasonable entry-level price. The 4060 needs two printed circuit boards for the CPU and not 15; it uses 64KB semiconductor memory cards, rather than the older core boards which stored half that amount. The design inc1ude.s a separate I/O processor (another PCB), there is a good deal of built-in self-testing, and the more compact approach means less cabling, less heat, and more reliability.
Higher up the range are the 4070 and 4080. They have a variety of memory, tapes and a greater expansion capability, though no 4000 model can have more than one megabyte of directly-accessible storage, a fairly low limit by comparison with some mid-range U.S. minis.
System software
There are three operating systems for the 4000. Although described by GEC Computers as different, they share some common functions - all are multiprogramming, too - and so can be regarded as an upgrade path. COS is a core-only system, DOS a minimal disc operating system but OS4000 is the one most users will meet outside the real-time environment.
A pioneer
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.
- Good memory integrity through use of base and limit (range} registers.
- Re-entrant code segments.
- Increased speed or memory mapping through the use of firmware for the nucleus.
OPUS, released in Autumn, 1975, is the principal GEC involvement in multi-access operation and is a packaged system based on the OS 4000 operating system, together with a selection of elements from the GEC hardware catalogue. It is now a proven mainline multi-terminal, timesharing system. which can support system development and run applications programs simultaneously. OS400 now is generally issued in the OPUS form.
OPUS supports up to 32 time-sharing terminals. They can be running interactively or they may be devoted to specific background batch jobs - like RJE, for which emulator packages are becoming available, or printer spooling. The principal OPUS/OS4000 languages are:
- Babbage: a high-level assembler. reportedly easy to use and to some extent compensating for the limitations of the register facilities of the; 4000. Commands largely follow English-language terms (IF ... THEN, RETURN, CALL). To some extent it follows the fashionable notions of structured programming; certainly it encourages a modular structure, with chapters linked into processes which form an application system.
- Fortran: a Fortran IV to ANSI 1968 standards. A single-pass compiler, it produces non-optimised object code. GEC has an extensive library of run-time and applications routines for it.
- Coral 66: a highly-rated implementation of the official blue book definition of this language. Used widely by MoD installations of the 4000.
- Algol: full implementation of Algol 60, compatible with that for ICL 4100 and 1900 systems.
- APL: recently-announced interpreter containing ,em>all the features of other commercially-available advanced APL systems,/em>. Features considerable reporting and debugging facilities; file support includes indexed sequential.
- Basic: the usual language for OPUS users. Apparently a fairly good implementation, with several of the normal enhancements including matrix-handling, string-handling. chaining and filing.
- RPG 2: a compiler which broadly follows the de facto standard laid down by IBM System/3.
- Cobol: not yet available; when it appears it should be a considerable boost to the commercial aspirations of the 4000. The compiler is being written by North Staffordshire Polytechnic and was scheduled for completion originally in Autumn, 1978. It is due to appear later this year. or perhaps during 1980.
- BCPL and RTL2: available through the GEC Computer Users' Group.
Other significant system software includes a sort-merge, an indexed sequential access method, and an 0S4000 enhancement to provide true transaction processing.
Undergoing field trials at a number of customer sites is an implementation of the Cincom Systems TOTAL package. TOTAL is the worlds' best-selling database manager and is available on several other computers. When it is tested fully and released for implementation on the 4000., TOTAL will add considerably to its attraction for applications involving large amounts of data organised in relatively complicated arrangements.
The company has commissioned a suite of commercial software, including sales ledger, purchase ledger, nominal ledger and payroll, now due to be handed over. The applications will have field trials in GEC Computers before being released.
Model Characteristics
| Model | Memory size (Kb) | Memory Type | Cycle time of memory in nanoseconds | |||
|---|---|---|---|---|---|---|
| Min | Max | Core | S/C | Mixed | ||
| 4060 | 64 | 256 | Yes | 550-600 | ||
| 4062 | 64 | 1024 | Yes | 550-600 | ||
| 4065 | 64 | 1024 | Yes | 550-600 | ||
| 4070 | 64 | 512 | Yes | 800 | ||
| 4080 | 32 | 256 | Yes | 550 | ||
| 4080M* | 32 | 256 | Yes | 550 | ||
| 4082 | 128 | 1024 | Yes | 665** | ||
| 4085 | 128 | 1024 | Yes | 550-600 | ||
* Miniaturised and ruggedised 4080
4-way interleaved memory of 32K blocks; each block has 800ns cycle, so the nominal cycle is equivalent to 665ns.
After this article, GEC produced a 4090 system in 1981 and some further systems in the period to 1987 at least.
| Model | Instruction times in microseconds (double precision in brackets) |
Floating point 32-bit operands | |||||
|---|---|---|---|---|---|---|---|
| Add | Multiply | Divide | Reg | Add | Multiply | Divide | |
| 4060 | 2.3 | 6.3(6.7) | (10.09) | 1.9 | 7.2 | 11.5 | 12.7 |
| 4062 | 2.3 | 6.3(6.7) | (10.09) | 1.9 | 7.2 | 11.5 | 12.7 |
| 4065 | 2.3 | 6.3(6.7) | (10.09) | 1.9 | 7.2 | 11.5 | 12.7 |
| 4070 | 1.6 | 4.1(6.35) | 7.1(20.85) | 1.8 | 6.45 | 11.65 | 20.15 |
| 4080M* | 1.1 | 3.6(5.85) | 6.6(20.35) | 1.55 | 5.8 | 10.9 | 19.4 |
| 4082* | 1.1 | 3.6(5.85) | 6.6(20.35) | 1.55 | 5.8 | 10.9 | 19.4 |
* all times for the 4082 are quoted using a nominal cycle time of 800 nanoseconds
Architecture
The instruction set provides operations on single bytes, variable-length strings of bytes, integers of 16 and 32 bits, and single bits within a 16-bit word.
The hardware supports multi-programming for up to 256 independently-scheduled processes; a set of hardware base and range registers (the Segment Registers) protect the store occupied by the component segments of the processes from unauthorised access by another process, while allowing the sharing of code and data between processes in a flexible and controlled manner.
Commercial Aspirations
GEC COMPUTERS has had interests in the commercial market with the use of the 2050 as an RJE terminal but with the continuing development of its systems software, particularly the multi-user operating system and the provision of new business-orientated languages, it hopes to gain some share of the market; although this might prove hard against fierce competition from the many systems houses already established in this area.
Business applications are reportedly being developed and GEC Computers certainly has links with a number or top software houses - Data Logic, Systems Designers and SPL. Smaller organisations looking to specialise on the GEC 4000 include Ian Martin Computers Ltd and John Bell Associates.
Processor and memory
| Word length | 16 bits |
| Addressing: direct, indirect, relative, indexed | 64K of virtual memory/process. Nucleus performs address mapping consisting of offsets to base registers for up to four current 16K segments. A process may have up to 255 segments but only four are current. |
| Registers |
|
| User microprogramming | No |
| Hardware floating point | Yes, as standard |
| Instruction set | 160, including floating point with special string and bit manipulations. |
| Instruction times in microseconds |
|
| Floating point in microseconds | See table |
| DMA |
Multiplexed I/O channel transferring at up to 300KB for autonomous half-word (16-bit) transfers or up to 900KB/sec at burst rates. External multiplexed channel, external disc/drum channel, for extra fast I/O processing at up to 2MB per microsecond. |
| Programmed I/O | Yes; semaphore drives I/O under program control if desired. |
| Maximum number of devices addressable | Nominally 256 |
| Main memory type | May be core or semiconductor, or a mixture of both (see table). |
| Mapping | Nucleus performs address mapping into current 64K of segmented virtual storage, using firmware. |
| Memory range | From 64KB to 1MB (see-table for details). |
| Increments |
Core in 32KB increments, semiconductor in 64KB increments. The 4082 needs 4 × 32 = 128KB increments, because of four-way inter-leaving. |
| Cycle times | 550-600 nanoseconds (see table for details). |
| Memory protection | Yes, using base and limit on access to segmented memory. |
| Error correction | Nucleus provides error trapping and failed processes can be re-scheduled or hung up. Semiconductor stores use Hamming codes for single error-correction and double error-detection. |
| Parity checks | Yes and CRC on communications lines |
| Cache memory | No |
| Proven but not outdated architecture | Conceptually sound |
| Part of compatible range | Yes |
Mass storage
| Disc | -Purchased -cartridge: 4-8MB removable/fixed; transfer rate using interlaced sector transfers = 123KB/sec to normal interface. Four drives per controller -fixed discs: 35MB and 70MB, four drives per controller. 270MB disc has been proposed. |
| Drum | -head per track -1, 2, 4MB capacity Transfer rate varies between 110KB and 440KB per second, depending upon interface. |
| Mag tape | 9-track, 800bpi and 1600bpi and switchable; transfer rate 30Hz |
| Cartridge tape | Available |
Terminals
| Max no per system | Under OS4000 using transactional environment, 64; multi-access users, 32. Local attachment up to 300 metres. |
| Long line drivers | Not provided by GEC, but accommodated easily |
| Interfaces available | RS232, V24 |
| Attitude to OEM terminals | Driver software has been designed around own terminals. GEC will accommodate OEM terminals but makes it clear they are the user's responsibility. |
| Easy attachment of extra/or non-standard terminals | Interface contention unit provides ability to add extra Teletype-compatible terminals. A variety of communications controllers allow attachment of other non-standard terminals. Non-standard in GEC-parlance usually means only terminals for which GEC does not provide documentation, service support, cables or controllers, so connection is at owners' risk. |
| Communications and Teleprocessing Communication |
Extensive range of communications controllers is available, including: -inter-processor links -four-channel comms controller -full range of barrier protocols approved by Post Office -RJE to IBM (HASP) -front-end processing for ICL 1900 series by emulation of ICL 7903 communications processor - GEC is working on X25 to provide a micro-based controller for 9,600 baud. Available now is the middle High Level Data Link Control (HDLC) link to link protocol. -can support CAMAC: interfaces for A/D converters. |
| Teleprocessing | Multiform 4000 screen formatting and file manipulation software is available. |
Other peripherals
| Printers | Dot matrix 80 col 100cps -132 col 165cps Line printers -136 col 300lpm -136 col 60lpm -136 col 1,250lpm Thermal printer -300 cps |
| Paper Tape | 700cps reader, 350cps reader, 110 cps punch |
| Card | 285 cpm reader, 600 cpm reader |
System software
| Operating systems | COS - real-time multiprogramming operating system
for core-based systems only. DOS - Disc operating system for similar real-time and process control work. Features multiprogramming, overlays, user-defined partitions OS4000 - most sophisticated operating system both for program development and applications featuring: -multiprogramming -overlays -time-slicing -output spooling supports batch, transaction processing, multi-access, RJE and combination of these environments being set up at system generation time. All 4000 processors have a built-in hardware real-time executive called Nucleus, which performs the following functions: -address mapping -message passing -scheduling -I/O control -semaphore handling. |
| Principal system software other than OS | Index Sequential Access Method (ISAM) Information retrieval (STATUS II) Data Base Management (TOTAL) GINO-F Utilities: sort merge, macro generators MGEN and MLI, text editor, PERT, multiform 4000 |
| Digital plotter | 35 and 90cm drum plotters; interface and support software available for Versatek range of printer/plotters |
SAMPLE PRICES
GEC prefers to quote prices for specific customer requirements. Competition in business and commercial computing may mean the policy will change. Prices here were quoted last month to Computermarket visitors.
Standard Configuration
GEC4060 System 1
- 128KB store (semi-conductor)
- 4 channels for terminals
- console device - with control
- 4.8 + 4.8MB cartridge disc
- Dot matrix printer 165cps/132-col
- OS4000 Transactional multi-access and batch environments
- RPG II and multiform-handling software and VDU handling
£33,350 plus £3.300 maintenance
System 2
- 192KB s/c
- 8 channels
- console device
- 2 × 35MB disc
- line printer 300 lpm/136-col
- OS4000 Transactional multi-access and batch
- RPG II and Multiform and VDU handling software
£53,000 plus £5,875 maintenance
System 3
as System 2 but :
- 256KB s/c
- 16 channels
- 2 × 70MB discs
- 600 lpm lineprinter
- same software
£63,380 plus £7,300 maintenance
GEC 4065 System 4
- ½ Mbyte
- 32-user system
- 4 × 70MB discs
- 600 lpm printer
- 800bpi 9-track mag tape
- RJE to IBM with synchronous COMS controller
- Fortran, Basic, RPGII, OS400
£120,750 plus £12,600 maintenance
GEC 4085 System 5
- 1 Mbyte s/c
- 64 transactional users
- 4 × 70MB discs
- 2 × 600 lpm printers
- 1 × 800 bpi mag tape
- 1 × 1 Mbyte drum
- operating system and Babbage, Fortran, Basic
£214,000 plus £17,800 maintenance
Prices do not include VDUs, which should cost around £1,000 per unit.
CONCLUSIONS
- The 4000 is from a reliable British manufacturer with good maintenance support. The computer has a good reputation for reliability and maintainabillity - "an engineer's dream".
- GEC has a good reputation in real-time/process control and communications markets, where it clearly has a good future. The GEC 4000 range is unlikely to compete effectively in the commercial market with American machines, though, until Cobol and to a lesser extent TOTAL become available.
- The languages available are generally well-regarded, though, even if they are not well-suited for business applications. Babbage has its enthusiasts and Coral 66 is rated very highly on the 4000.
- The internal use of the IBM standard BCD numbering can be inconvenient, as it gives the exponent in powers of 16. Where good precision is required, for example in simulation, this forces you to go to double precision arithmetic and hence reduces the speed of execution. In other circumstances, though, BCD is a perfectly adequate number representation.
- The availability of various communications channels and protocol handlers is one of the strengths of the machine and to some extent compensate for the relative slowness of execution for some CPU operations.
- The register structure of the series is fairly limited and the lack of a stack facility does not help in recursive language implementations.
- There is no writeable control store or fast-access cache memory but the 4082 has the facility to inter-leave memory, which helps optimise throughput. All memory access is via offsets to segment registers, which slows overall execution speed, and with the relatively small maximum memory size, very large programs will require a good deal of swapping.
- A fairly complex SYSGEN procedure is provided. It will suit only the experienced user.
- The editor is poor, allowing only forward line edits.
- With a 165cps printer, a VDU, one 9.6MB disc, 128KB memory, and RPG, you can have a 4060 for around £34,000. That sounds costly to us for an entry-level system but further up the scale the prices look much better; three VDUs and two 9.6MB drives sell for about £45,000; two 35MB disc pack drives with a 300 lpm printer and 192KB cost around £54,000, though that includes only one display terminal.