Elliott 503


Elliot 503 and Tasmania

An Elliott Brothers (Elliott-Automation Group or Elliott Computing Division) model 503 "ULTRA HIGH SPEED DIGITAL COMPUTER FOR SCIENCE AND INDUSTRY" was installed at the Hydro-University Computing Centre (HUCC), Hobart, Tasmania in January 1964, with commissioning tests conducted in May 1964. The machine appears to have been operational shortly afterwards, either June or July 1964 (ref: minutes of the Hydro-University Computer Board, Director's Report 22-Jan-1971).

The HUCC Elliott 503 operated from 1964 until 1977, a fourteen year stretch. In September 1975 a Burroughs B6700 was installed as a replacement for the Elliott 503. This commissioning date was later than planned due to ongoing building delays as the Burroughs and the supporting University Computing Centre was located in a new purpose built building.

Even in late 1977 the Burroughs B6700 was using the plotter attached to the Elliott 503 as an output device (in conversation with Rod Bilson 4-March-2010 and clarification from Brian Marriott).

Elliott 503 RAP (Reserve Area Program)

The RAP is the operating system of the Elliott 503.

Michael Miller's annotated copy of RAP

From Michael Miller (UK) comes a copy of the Elliott 503 Reserved Area Program (RAP), a critical piece of Elliott 503 software infrastructure. Many thanks to Michael for preserving this valuable and essential piece of Elliott 503 history.

Elliott description of RAP

The Reserved Area Program, in conjunction with the MESSAGE button, provides a means of controlling the 503 computer. Communication, between the operator and the computer, is through a directly coupled, electric typewriter. Pressing the MESSAGE button causes an entry to the RAP which then expects a message.

The RAP is read into locations 7936 - 8165 of the computer store by the fixed instructions contained in locations 0-3. The locations 7936 - 8191 form the reserved area of the store and the protection of this area can be removed by depressing the 'NO PROTN' button the control console (see 1.2.1)

The RAP contains an Input routine which will read a relocatable program tape and place the program in the first available space at either end of the available store. Provision is made for several programs to be in the computer store at the same time and communication between such programs is facilitated by means of a system to which each program is linked on being stored. Each program is called by a name, which is held in the program itself, and hence the user does not need to know the stored position of any program. The RAP provides a means of entering the programs so held, and when the running of a program is completed, control of the computer returns to the RAP, where it remains until the next message is received through the typewriter.

Michael describes his Elliott experience:

My experiences with the Elliott 503 (1965-66)

On graduating from Cambridge, I joined the Post Office Research Station at Dollis Hill in July 1965 and was almost immediately sent on an Elliott Algol programming course so that I could do some simulation studies on the frequency stability of digital communications networks – the foundation of today’s global network!

I had about 25% of the available time on the DH 803 machine, sharing with a guy (André? Deutsch) who was doing character recognition for postcodes! Everything was done by paper tape and Friden Flexowriter.

The program output was a collection of numeric data showing the shifts in frequency over time. This needed plotting, which the Drawing Office refused to do. So the work was transferred onto the 503 at 2-12 Gresham Street (PO Engineering’s HQ) in preparation for production runs on the 503 at Elliott’s factory at Borehamwood, which had a plotter.

The PO’s 503 was mainly used for teletraffic simulations, using the Elliott Simulation Package (ESP) – in effect, “if 100 calls arrive at random times, how many will get through a busy network of so-many lines between London and Birmingham”. It had a core backing store of 64k words of 39 bits.

The Borehamwood machine cost a whole SIXTY pounds (£60) per hour in the ”cheap rate” between 0100 and 0300. As this was 10% of my annual pre-tax salary of £600, that was all I was allowed access to. In all, I must have had over 12 hours use of that machine.

My program, which I developed in 1965-66, took about 20 minutes to calculate a collection of data and a further 20 minutes to plot it out. The interface was the Elliott Plotter Package with a few ALGOL procedures such as PENUP, PENDOWN, DRAWLINE(x,y), MOVEPEN(x,y) etc. These were implemented as sequences of ELLIOTT(a,b,c,d,e,f,g) procedure calls.

It occurred to me that if I could modify the plotter package to place the “up, down, north, east, south, west” commands in the backing store and use the interrupts on the 503 to tell me when to pull the next plotter action out from a circular buffer I could double my machine productivity. I used ELLIOTT instructions to set interrupt masks and so forth but found that after a short period of productive plotting the interrupts were turned off and my program stalled.

Accordingly I dumped out the RAP into a binary array, converted it to machine code and spent many train journeys to and from the office looking over the code to understand it.

Amongst other joys I discovered a machine code procedure which took whatever was in the accumulator, placed it in a spare location in the Re
served Area and then executed it, bypassing the lockout on writing into the RAP storage area except when in supervisor mode!

Eventually I did get the multi-programming to work, but by then was convinced that an analytical approach was needed to solve the synchronisation conundrum (“Could a stable network be built”) and spent the next 3 years at Warwick University (Sept 1966 to Aug 1969) getting a PhD on that quest. 

Elliott 503 brochure

Thanks to Eric van der Meer for finding.

Elliott 503 FACTS

Thanks to Brian Marriott for locating this copy.

Elliott 503 production numbers

Somewhere between 33 and 39 Elliot Brothers model 503 computers have, so far, been identified (recorded) as delivered worldwide. This total is approximate due to the following factors:
  • Two lists of deliveries have been found sourced from Elliott Automation, however the customer names and delivery dates (at the year level) are in conflict between the two lists (see customer deliveries below).
  • Both lists cover differing periods up to (possibly the end of) 1966.
  • The Elliott 803C was understood (from a post in alt.folklore.computers) to be a 503 under the "skin" and could be field upgraded to a 503 - whether these upgrades were ever included in the lists referenced above or otherwise documented is unknown.
  • An additional machine from 1967 (listed in UK Hansard) has been listed at Surrey University. Elliott Brothers merged with English Electric in 1967, so this year may have been the lat year the Elliott 503 was manufactured or delivered. Surrey University was Battersea College of Advanced Technology prior to 1966 (Thanks to Simon Lavington for clarifying).

Elliott 503 customer deliveries

Elliot 503 delivery details 1963 through 1966, information extracted from CCS-E4X5 compiled by Our Computer Heritage. A total of 32 machines delivered during the period of 1963 to 1966.

A second list, in French, with the title "INSTALLATIONS NCR-ELLIOTT 503 Sept. 64" has been found and differences/additions noted below with tag FL64. This document lists the following machines which were not listed in the CCS-E4X5 document:
  1. Skoda Motors (Czechslovakia)
  2. Samuel Fox (United Kingdom)
  3. Insitute Ruder Boskovic (Yugoslavia)
  4. Research institute unknown (Poland)
  5. and an additional 6 machines used by NCR-Elliott
Simon Lavington helpfully noted that FL64 appears to have Elliott 803 machines mixed in with model 503 which would explain the overlap and confusion between the two lists.

 Date  Where Customer  Application Click pictures for larger size
1963 United Kingdom Elliott-Automation Ltd Service bureau  
    NCR  Service bureau   
    Elliott-Automation Ltd Service bureau   
1964 United Kingdom United Steel Co Ltd  Operational research production scheduling
Installed at Cybor House, Sheffield
Picture from the Journal of Simulation by BW Hollocks.

The "...or" in Cybor House stood for Operational Research. "Cyb.." was for Cybernetics.

"...later in 1964 Cybor House installed an Elliott 503 (Figure 9) to replace the Pegasus, but initially using the old Pegasus magnetic tape drives. Tocher had to design and lead the building of an operating system for the new machine since one was not forthcoming from the manufacturer. The 503 was then used as the platform for the development of GSP Mk.3 which was released in 1967 (Tocher, 1967)."

  The Netherlands ABW/TNO Government computing centre for industry   
  Australia Hydro-University Computing Centre  University of Tasmania
Hydro-Electric Commission

Scientific computing centre, Hobart Tasmania

One example use of this machine was to conduct finite-element analysis to optimise the amount of cement needed to construct dams used in hydro-electricity generation in Tasmania. The cost of the machine was recouped many times due to the reduction in the amount of construction materials.
  The Netherlands Rijkswaterstaat Land reclamation calculations  
  Italy NATO FL64: La Spezia, city in northern Italy.  
  United Kingdom Army Operational research   
  United Kingdom Aircraft & armanents experimental establishment Evaluation of aircraft performance  
  United Kingdom Bristol University Crystallography and general research   
  Federal German Republic  NCR  Service bureau   
  USSR  Soviet Academy of Science  Scientific computing   
FL64FinlandUniversity of Helsinki / Finnish Cable CompanyOnly listed in FL64 document 
1965  USSR  GOSPLAN System simulation studies  
  United Kingdom  Short Brothers & Harland Ltd  Analysis of flight test data  
  Finland  State Computing Centre  Government  
  New Zealand DSIR Department of Scientific and Industrial Research Meteorological analysis and highway design

DSIR, Victoria University of Wellington and Burroughs B6700
  United Kingdom Rocket Propulsion establishment Analysis of rocket firing and design of rocket motors  
  United Kingdom  Mullard Ltd  Electroncis and physics research   
  United Kingdom  General Post Office  Operational and communications research
FL64: 32,000 words of auxiliary memory, 2 printers, 6 magnetic tape units.
Michael Miller notes reference the Post Office HQ is at 2-12 Gresham Street and where the 503 was located. The 503 was mainly used for teletraffic simulations using ESP (Elliott Simulation Package). MM notes that the "...core backing store of 64k words".
  United Kingdom  Elliott-Automation Ltd  Research and development   
  United Kingdom  Battersea College of Advanced Technology  Education and research
This institution later became the University of Surrey and is referenced in the March 1967 Hansard, HC Deb 06 March 1967 vol 742 cc201-5W  
  Israel Technion Institute of Technology  Teaching and research, FL64: Haifa Technion  
  Federal German Republic Prakla GmbH Geophysical surveying and prospecting calculations  
  German Democratic Republic Institute for Data Processing Economic planning and scientific research
FL64: University of Wittenburg/Halle (Leipzig), 2 readers/punches, 4 magnetic tape units, 16,000 words of auxiliary memory.
  Czechoslovakia Kancelarske Stroje Computing centre for economic planning   
1966 Netherlands Rescona Civil and structural engineering  
  Overseas Undisclosed Undisclosed  
  United Kingdom Elliott-Automation Ltd Systems development   
  United Kingdom  Elliott-Automation Ltd  Radar research   
  United Kingdom  EMI Electronics Ltd  Research   
  United Kingdom  Satchwell Controls Ltd Data processing, planning and research  

Tony Hoare (email: 11-May-2010) noted that an Elliott 803C was delivered to Harland and Wolff (Belfast Shipbuilders), and subsequently passed to the electronic engineering department at Queen's University Belfast where it was used by Professor Ryan.  Tony subsequently caught up with this machine and provided technical advice to Professor Ryan when Tony joined Queen's in 1968.

Elliott 503 description

1969 description of Elliott 503

The 503 is the most powerful in the present range of the Elliott solid state computers. While primarily designed for scientific work it is fully adaptable to commercial applications. It is very fast and is capable of controlling a large range of peripheral devices.

First Installed: 1963
Present Availability: 6 months (1966)
Country of Manufacture: Great Britain
Selling Price: £56,000 to £416,000
Rental per month: £1,017 to £9,200
Amount of initial charge: Nil
Purchase Option conditions: None
Installation cost: Included in price.
Carriage: Included in price
Warranty: 6 months

Physical Characteristics:

Floor area average complete system: 600 sq. ft.
Maximum floor loading: 250 lbs. per sq. ft.
Power requirements: 9.2 - 35 kVA.
Air conditioning requirements:
70 +/- 4 deg. F, 40-60% RH, 95% efficient @ 10 microns

Central Processing Unit Used: 503

Special features which can be added to Central Processing Unit: Interface Matching Unit

Operation Times:

Addition (fixed point): From 7.2 usecs.
Multiplication (fixed point): From 34.8 to 46.8 usecs.
Division (fixed point): From 68.7 usecs.
Addition (floating point): From 13.2 to 30.3 usecs.
Multiplication (floating point): From 31.5 to 41.0 usecs.
Division (floating point): From 60.9 to 61.8 usecs.
Cycle Time:
 Logic ) 3.6 usecs
 Storage) 3.6 usecs

Word Length: 39 bits including sign (each 39-bit had an extra bit for parity)

Basic Storage:
Type: Ferrite Core
Size: 8192 words

Additional Storage:
Type: Core
Size: 131K


Magnetic Tape Handlers Speed: 60,000 ch/sec.
Line Printers Speed: 330/1250 l.p.m.
Magnetic Film Handlers Speed: 4300 c.p.s.
Card Read/Punch Speed: 300 c.p.m.
Card Reader Speed: 340 c.p.m.
Graph Plotter Speed: 3" per sec, accuracy .01"
Typewriter Speed: 10 c.p.s.
Paper Tape Reader Speed: 1000 c.p.s.
Paper Tape Punch Speed: 100 c.p.s.

Software Available:

Elliott Autocode
Symbolic Assembly Code (SAP)
Fortran to Algol Translator
Input/Output System
Simulator Language
Time Sharing
Fortran IV
over 200 library and complete application programmes.

System Analyst Service: Not available
Programming Service: Not available
General Comments:

Same instruction code as 803 but speed of operation is nearly 100 times greater. There are a number of interrupt lines which not only permit running of programmes in parallel but also are used in connection with on-line operation of the 503.

Selling Organisation in Great Britian: Elliott Automation Computers Ltd.


Elliott 503 ALGOL versions

503 ALGOL Mark 1
503 ALGOL Mark 1 + MODs
 - MOD 2 - Arrays on core backing store
 - MOD 3 - Lineprinter facility
 - MOD 5 - Editing facility
 - MOD 8 - Segmentation facility
 - MOD 9 - Segmentation using magnetic tape
 - MOD 11 - Improvement of machine code facilities
 - MOD 12 - Standard procedures modification
503 ALGOL Mark 2 - never delivered - part of the ill-fated Elliott Mark II software project
503 ALGOL Mark 3


Early British Computers - A description of the early beginnings of Elliott Brothers with pictures. 

Elliott 503 Project ToDo list

Elliott 503 Project ToDo list - big list of things to do, ideas, wishlist, and some of what has been done so far.
  1. Contact all the customers identified as receiving 503s to see if any artifacts still exist.
  2. Find user developed software for the 503 - particularly interesting would be the list processing software, the UK economic simulator, etc.
  3. Find more photographs of the 503 and peripherals.
  4. Develop a 503 specific simulator (probably based on an existing 803).
  5. Digitise paper tapes - Brian has at least one of the ALGOL tapes, this digitised version can then be compared with the 803 ALGOL that Bill recovered.
  6. Reconstruct an annotated listing of the ALGOL compiler - perhaps based on BillP's work.
  7. Construct a catalogue of all the documentation - there are multiple versions of some documents.
  8. Find a copy of FEAT - the FORTRAN to ALGOL translator.
  9. Finish photographing the engineers display and console typewriter.
  10. Obtain replacement RETURN Key for IBM Type 13 console typewriter.
  11. Develop a detailed description of the 503 and its differences to the 803.
  12. Attempt to discover more about the Elliott 803C model which is claimed to be a 503 under the skin and field upgradeable.
  13. Find and recover the Elliott User Program Library.
  14. Schedule a visit to UTAS to view and scan the UCC scrapbook of old photos.
  15. Research the history of the 503 at UTAS - Brian has found a lot of material which will help with this particularly its role in fine-tuning the Hydro's dam construction projects.
  16. Construct a timeline for the 503 in Tasmania.

  1. Over 1,500 pages of documentation scanned by Eric van der Meer.
  2. More documentation found and scanned by Brian Marriott.
  3. Contacted TMAG about the two missing hardware volumes.
  4. Host the documentation currently scanned, see www.retroComputingTasmania.com/documents
  5. A copy of Reserved Area Program (RAP) now located - thanks to Michael Miller and Peter Onion.
  6. Write to Tony Hoare to get more details on the software history. Tony introduced Simon Lavington who is currently completing a history of Elliott Brothers computers.
Nigel Williams,
May 12, 2010, 8:20 PM