This is the original 2050 Sales Brochure dating from 1971. Note that the machine is called the MECS 2050 throughout, as the company was called Marconi-Elliott Computer Systems Limited at the time. The following year, the company was renamed GEC Computers Limited, and the 2050 became known as the GEC 2050. The logo below appeared on the first 2050's, but was replaced with the more familiar "GEC 2050" in a blue rectangle.

Forward references:
Description- the CPU, I/O, and Store systems
Specifications - System sizing, Timings, Register widths, Store, I/O, etc.
Software - 2050 based and simulation
Registers - and ALU interconnections
Peripherals - Paper tape, Teleprinter, Lineprinter, Thermal console, Discs, Terminals

MECS 2050 logoFeatures

Low Cost High Reliability Modular Architecture

The MECS 2000 range provides the user with an extremely powerful, low cost, real-time computing system and incorporates major technical developments in microelectronics, which lead to a high degree of reliability. The very latest techniques in computer architecture have been applied resulting in a high degree of modularity. Applications range from the solution of problems in simple control to the complex needs of Data Communication systems.

Comprehensive Software Package, System Simulation

In the design of the MECS 2000 range the software needs of the user are seen to be of paramount importance. Comprehensive software exists to enable the user to make the most efficient use of the system. The heart of this software is a unique system simulation program written in FORTRAN and suitable for use on the majority of large computers. This allows system development to proceed before making a commitment to the hardware. An ASSEMBLER, PROGRAM CHECKOUT SCHEME, LINKING LOADER, TEXT EDITOR and DEVICE CONTROL ROUTINE are also available to minimize system commissioning time.

MSI Powerful Instruction Code

The use of integrated circuit Read Ouly Memory (ROM) gives the MECS 2050 a rich instruction code. Such operations as MULTIPLICATION, INDIRECT BRANCHING and AUTO INDEXED ADDRESSING are all carried out by this advanced hardware at no extra cost.

Multibyte Manipulation

Arithmetic calculations and data manipulations can be performed on operands of varying lengths which can be specified by a program instruction. This gives MECS 2050 an effective word length of 32 bits.

Four methods of data transfer

MECS 2050 input-output systems give the user tremendous flexibility. PROGRAMMED INPUT- OUTPUT is no longer a limitation. In addition, MECS 2050 offers AUTONOMOUS SINGLE and AUTONOMOUS BURST modes of data transfer together with DIRECT MEMORY ACCESS in any order and combination to satisfy the needs of the application. Data transfer rates of up to 800 kilobytes per second can readily be achieved. A powerful interrupt handling and identification facility is provided for real-time applications.

Power failure detection and restart

In the event of a power failure, the MECS 2050 can organize its internal operations so that, when power is restored, the system may continue as if the power failure had never occurred.

Extensive range of peripheral devices

In keeping with the progressive policy of covering the real-time computing field, an extensive range of peripheral devices is offered to give complete coverage of the wide variation of systems requirements.

British made: Fully supported

The products designed and manufactured by Marconi-Elliott Computer Systems are supported by a vast organisation of expertise which provides channels of constant liaison between the Company and its customers.


The MECS 2050 computer system has not only been designed to be modular in concept but also in physical construction. This modularity offers immense benefits for field maintenance and system expansion.

Advanced integrated TTL circuit techniques, employing MSI, are used throughout. A central processor, normal interface facilities, Input/Output modules, and a store with its own control logic can all be accommodated in the basic computer unit.

Three of the four methods of data transfer are implemented by this NORMAL INTERFACE which is standard throughout the MECS 4 series of computers and offers the benefit of computer compatibility with a standard range of peripheral devices. The transfers provided in the basic computer unit are Programmed, Autonomous Single, and Autonomous Burst. Programmed, the conventional data transfer, takes one or two bytes to or from the bottom of the accumulator. Two instructions initiate programmed transfers; IN and OUT.

Autonomous Single data transfers take place to or from allocated areas of main store and once initiated by a programmed transfer continue independently of the program, interleaving on up to 64 way addresses at any one time. Transfer rates of up to 85 kilobytes per second can be achieved using this method.

Autonomous Burst data transfers operate at data rates of up to 385 kilobytes per second on only one way address at a time.

The fourth method of data transfer is by Direct Memory Access which is offered as an optional extra to the basic computer unit. In this method data transfers take place directly across the store highway at rates of up to 800 kilobytes per second.

Interconnections are kept to a minimum by the use of large printed circuit boards which plug directly into printed circuit back-wiring planes.

The mechanical construction conforms to standard 19 inch rack mounting specification and units have the following dimensions: front panel 483 mm (l9in.) wide, height 267 mm (10&fract12; in), depth 534 mm (2lin.). Each rack is self-contained, incorporating individual cooling fans and power supplies.

Extensions and modifications are easily accomplished by simply introducing new modules or re-arranging an existing configuration to suit the current requirements of the system.

The control of the MECS 2050 computer is facilitated by a simple control panel. Three lamps indicate POWER ON, PROCESSOR STOPPED (illuminated whenever the processor is in the HALT state) and SIGNAL (this lamp may be lit or extinguished by program instructions). Switches control essential functions such as POWER ON/OFF, processor RUN/HALT, RESET and INITIAL PROGRAM LOAD. A key operated switch is provided allowing the system to be left in a state where all switches except POWER ON/OFF are disabled. A SENSE switch is also provided which may be tested by program instructions. A versatile control and monitor unit is offered as an optional extra when full system control is required.

Operational temperatures are in the range 0 C to 55 C with humidity in the range 0% to 95% R. H. The supply requirement is 220 to 250 volts single phase with a frequency of 50 or 60 Hz.

MECS 2050 Computer Specification

Byte length 8 bits
Word length 4 bytes
Half word 2 bytes
Operand length 1, 2, 3 or 4 bytes
Instruction length 1 or 2 bytes
Program Accessible
1 Accumulator 4 bytes
3 Index registers 2 bytes
Sequence control register 2 bytes
Control register 1 byte
Program Inaccessible
Store buffer register 2 bytes
Store address register 2 bytes
Instruction register 1 byte
Scratchpad Address Register 4 bits
ROM address register 1 byte
ROM output register 2 bytes
Type Medium scale integrated circuits
Width 1 byte
Operation Parallel, twos complement
Microprogram Type Integrated circuit Read Only Memory
Type Magnetic ferrite core store
Operation 3D coincident current
Width 1 byte
Speed 950 ns cycle time
Minimum size 4 kilobytes
Maximum size 64 kilobytes
Units of Expansion 8 and 16 kilobytes
Types Programmed
Autonomous: Single Mode
Autonomous: Burst Mode
Direct Memory Access
Programmed 256 devices
Autonomous 64 interleaved transfers
Direct Memory Access 2 channels
Programmed 1 or 2 bytes/Instruction
Single mode from store 85 kilobytes/second max.
Burst mode from store 385 kilobytes/second max.
Direct Memory Access 800 kilobytes/second max.
Interrupts 255 device interrupts
Program levels Two, Base and Interrupt
Initiation of Interrupt Hardware or Software
Mounting 19in. rack
Size of single unit Width 483 mm (19in.)
Height 267 mm (10½in.)
Depth 534 mm (21in.) from mounting panel
583 mm (23in.) overall
Weight 41Kg (9Olbs)
Power supply voltage 220 to 250 volts + 10%
Frequency 50 or 60 Hz + 4%
Power consumption with 8KB store 0.5kVA (excluding input/output modules)
Temperature Range
Operational 0ºC to 55ºC Cooling air temperature
Non derangement -40ºC to +70ºC
Operational 0 to 95% RH without condensation
Cooling Fans draw cooling air through the unit from front to rear


The MECS 2000 range is offered as an integrated system comprising low cost hardware and comprehensive, compact software.

An impressive selection of program development aids, written in assembly language, is provided for use on MECS 2000 machines. In addition an advanced support software package has been produced for development and proving of MECS 2000 systems using either on line or batch processing facilities on any machine offering FORTRAN IV.

An important feature of MECS 2000 range software is the ease of enhancement or adaption to suit particular user needs. This is especially valuable when extending the MECS 2000 real-time simulation system which is the heart of the support software package, to cater for system design studies or to simulate a proposed system configuration prior to a hardware commitment. Also, system designs may be investigated in detail without the delay or expense incurred by the use of sp ecially configured MECS 2000 hardware.

Flexibility is also a prime concept of the MECS 2000 assembly language. The language has been designed to enable the user to achieve maximum efficiency in speed and store usage. At the same time, many features are included to aid the program mer to produce error free programs in the minimum time.

During program testing, powerful interactive debugging aids are available to the programmer on both the MECS 2000 range computers and in the support software package. These aids, coupled with text editing and macro-generation facilities, result in significant reduction in total program development time, without any adverse effects on resulting program efficiency.

Finally, the flexible design concept is again illustrated by a common approach to peripheral device handling routines and associated unit test programs. This ensures that the units are tested under realistic conditions and allows all test programs to be integrated into system tests, under control of an executive. Similarly, the device handling routines are ideally sulted for dedicated Input/Output applications where efficiency is of prime importance and at the same time they present a unified interface for use with a central interrupt control.

MECS 2000 Software includes:

(a) Symbolic representation of machine instructions, operands and program/data names
(b) Powerful set of data definition facilities
(c) Program and data structuring statements
(d) Independent assembly of source code modules into relocatable object modules.

(a) The capability of linking together relocatable object modules to form a complete program
(b) Interactive control of tape preparation/loading tasks using a comprehensive control language

(a) Interactive debugging aids for program development
(b) Control of program development using a powerful control language with error reports designed to give maximum help to the user in tracing program faults

(a) Operations either in conjunction with the Symbolic Assembly Program or as an independent facility
(b) General string editing, not pure line editing

(a) Input/Output control for each of the standard range of peripheral devices
(b) A unified interface to a central interrupt control program

forming the nucleus of real-time systems based on MECS 2000 machines

allowing integrated control of unit test programs in any standard MECS 2000 hardware configuration


(a) Operation either in conjunction with the Symbolic Assembly Program or as an independent facility
(b) Language independent text handling

MECS2OOO Support Software Package Implemented in FORTRAN IV includes:

(a) Simulation of MECS 2000 processor and peripherals
(b) Simulation of real-time interaction by use of an event simulator
(c) Utility routines to aid the user to develop and evaluate his MECS 2000 real-time system.

providing similar facilities to the MECS 2000 version in assembly language but designed to take advantage of big machine facilities where they are available.

offering facilities identical to those for the MECS 2000 versions and allowing simple transfer of programs from the support machine to MECS 2000

offering facilities identical to those for MECS 2000 version

The MECS 2050 Register System

Key to Registers used

Symbol Representing Length
A Accumulator 4 bytes
AM Most significant half of accumulator 2 bytes
AL Least significant half of accumulator 2 bytes
S Sequence control register 2 bytes
X1 Index register 1 2 bytes
X2 Index register 2 2 bytes
X3 Index register 3 2 bytes
P Length register 2 bits
C Control register 1 byte
Q Address of operand (q) 2 bytes
D Address byte of instruction 1 byte
q Operand. The operand can be
1, 2, 3 or 4 bytes long specified
by the program instruction.
l = 1 byte (p = 00)
l = 2 bytes (p = 01)
l = 3 bytes (p = 10)
l = 4 bytes (p = 11)

[original document contains instruction set details here]

Training and Support

It is a policy of Marconi-Elliott Computer Systems that all products are supported by comprehensive customer training as well as hardware and software maintenance


A well equlpped Education Centre exists at Borehamwood and operates frequent "Standard Courses" covering the programming, engineering, and maintenance aspects of all products. Programming courses for the MECS 2000 range cover

(a) MECS 2000 range Software, including the assembly language and the full library of diagnostic and peripheral support routines.

(b) MECS 2000 range Support Software, including the system philosophy and the assembler implementation to enable the user to simulate his MECS 2000 computer on specified larger machines.

For customers wishing to maintain their own equipment, two levels of training are offered:-
(a) Hardware and system appreciation for executives.
(b) Full maintenance tralning for customers' staff.


Marconi-Elliott Computer Systems use the extensive facilities of the total GEC group of companies to offer maintenance and field support on a world-wide basis.

Maintenance on the low cost MECS 2050 can be achieved by the use of exchange units. This minimizes repair time when optimum performance and a low mean-time-to-repair (MTTR) are necessary.

For optimum system performance a comprehensive maintenance scheme can be adopted. However, alternative servicing arrangements can be offered and the schemes fall into the following categories :-

(a) Fully comprehensive service, on a 24 hour basis, to cover routine service visits, emergency on-call service and free replacements of all components and materials

(b) Fully comprehensive service as above but restricted to normal. working hours (9 a. m. to 5 p. m.)

(c) 'On-call' emergency service, as a second line support to the customer's own maintenance team

(d) Spares supply to the customer's own maintenance team

(e) Base workshop facilities for returned units


Support is provided in the field for both software and hardware aspects of the MECS range of computers. The company's engineering and programming expertise are available to the user.

The Field Support Unit controls back-up services for maintenance and the department interfaces with the product divisions. on engineering problems.


All computers in the MECS 4 series have a NORMAL INTERFACE for data transfers between the computer and peripherals. The MECS 2050 interface is a subset of the NORMAL INTERFACE, being only 1 byte wide rather than 2. This concept of a NORMAL INTERFACE which is standard throughout the series means that systems can be made up by choosing suitable peripherals from the whole range.

The varied transfer capabilities of the peripherals enable the four modes of data transfer to be used to their full advantage.


These peripheral devices only represent a section of the full range planned for the MECS 4 series computers.

© 1971 Marconi-Elliott Computer Systems Limited

Reproduced with the kind permission of GPT Limited.

© 1997 Andrew Gabriel. All Rights Reserved. / Last revision 12 October 1997