Issue Number 86 Summer 2019 Computer Conservation Society Aims and objectives The Computer Conservation Society (CCS) is a co-operative venture between BCS, The Chartered Institute for IT; the Science Museum of London; and the Science and Industry Museum (SIM) in Manchester. The CCS was constituted in September 1989 as a Specialist Group of the British Computer Society. It is thus covered by the Royal Charter and charitable status of BCS. The aims of the CCS are: To promote the conservation of historic computers and to identify existing computers which may need to be archived in the future, To develop awareness of the importance of historic computers, To develop expertise in the conservation and restoration of historic computers, To represent the interests of Computer Conservation Society members with other bodies, To promote the study of historic computers, their use and the history of the computer industry, To publish information of relevance to these objectives for the information of Computer Conservation Society members and the wider public. Membership is open to anyone interested in computer conservation and the history of computing. The CCS is funded and supported by voluntary subscriptions from members, a grant from BCS, fees from corporate membership, donations and by the free use of the facilities of our founding museums. Some charges may be made for publications and attendance at seminars and conferences. There are a number of active projects on specific computer restorations and early computer technologies and software. Younger people are especially encouraged to take part in order to achieve skills transfer. The CCS also enjoys a close relationship with the National Museum of Computing. Resurrection The Journal of the Computer Conservation Society ISSN 0958-7403 Number 86 Summer 2019 Contents Society Activity 2 News Round-Up 10 Bringing Comfort and Style to Atlas 13 Edd Thomas English Electric and its Successors at Kidsgrove 17 John Wilcock A Mystery Picture Revisited 27 Dik Leatherdale CCS Visit to NAM-IP in Namur 28 Rachel Burnett 50 Years Ago ….From the Pages of Computer Weekly 31 Brian Aldous Forthcoming Events 35 Resurrection Subscriptions This edition of Resurrection is the last in the 2018-9 subscription period. BCS members and certain former BCS members (see www.computerconservationsociety.org/resurrection.htm for a detailed explanation) will continue to receive printed copies. Other CCS members may subscribe (or renew) for the 2019-20 period on the same page. Society Activity Analytical Engine — Doron Swade The sheet-by-sheet inspection of Babbage’s vast technical archive is now in the end game after some three years. The last progress update reported that Tim Robinson, in the US, working from the digitised images of the manuscripts, was close to completing a review of the known catalogued material in the Science Museum archive and that one of the final tasks was a scrape of a relatively small but potentially critical set of drawings that had not been catalogued or scanned the contents of which are largely unknown. Tim has spent a week in London going through this material. This material evaded the Science Museum’s scanning operation in 2011 largely because it was not listed in the catalogue prepared by the late Allan Bromley who compiled the first near-comprehensive record, published in 1991, of the Babbage technical archive. There have already been significant finds. The Notations for Difference Engine 1, dating from 1834, thought to exist, had never come to light. These have now been found and represent a crucial piece in the puzzle of the developmental trajectory of the symbolic language Babbage developed as a design aid, to describe and specify his engine, and used extensively in the development of the Analytical Engine. Equally significant is the discovery of what is thought to be the legendary Plan 28a, part of the most advanced design for the Analytical Engine. There have been references to Plan 28 and Plan 28a designs peppered through the late manuscripts and some design drawings, but the existence of this plan has never been confirmed. Bromley told me in the late 1990s that he questioned whether it had existed as a separate entity in the first place in which event ‘Plan 28’ may have been a federation of improvements added to previous designs. The survey so far has identified mis-titled drawings, single drawings that have two unrelated catalogue entries, and drawings known to exist from earlier scholarly work but not located. These findings are openly shared with the Science Museum archivists in what has become a model collaboration between content specialists and archivists. ICL 2966 — Delwyn Holroyd Most of the 2966 survived its long hibernation without any problems. The only casualty was the 7501 terminal, although that too has now sprung back to life before we could take any remedial action. It is of course entirely possible the fault will return in due course. 2 Resurrection Summer 2019 EDSAC Replica — Andrew Herbert During the re-roofing of the First Generation Gallery at TNMoC the machine suffered no damage. Alex Passmore has made a number of upgrades and improvements to the power supply and power distribution. We now have an HT isolating switch on each rack to help us hunt down short circuits and two -50V DC power supplies, as required by the revised bistable design being used in critical areas. Power is also supplied to the operators’ desk. Les Ferguy and Peter Lawrence have tidied up the wiring of clock and digit pulse distribution. At the same time Les has begun labelling the ends of signal wires with unobtrusive slip on tags to deal with the problem of accidental disconnections. (In the original EDSAC wires were soldered to tag strips for security: during commissioning we have relied on mechanical fastons and these can fall off.) In addition Les has made improvements to the internal screening of the clock pulse generator chassis (and the spare) which has made it easier to set and adjust the operating frequency. Chris Burton continues the development of the clock monitor unit. Nigel Bennée took parts of the arithmetic unit home to Cambridge for upgrade and returned them to the machine. Peter Linington has continued testing the main store delay lines, driving them through the store access logic and main output bus. The main control commissioning team (James Barr, Tony Abbey and Tom Toth) have resumed their work. Having shown EDSAC cycling on executing a single X (no-op) order in location zero of store, the next step is to enable the sequence control system to allow execution from consecutive locations. The team has been having some problems with the clock and digit pulse setting. These include being able to make fine adjustments to the clock to obtain the correct delay in the main store, jitter, drift as the machine warms up, incorrect amplitude and shape of pulses. The clock pulse generator has had several improvements to deal with these issues and Chris Burton has constructed and installed the Clock Pulse Monitor chassis to enable setting to the correct frequency for the store. Issues about pulse shaping remain which may require some adjustment of how we distribute the various clock signals around the machine and further possible improvements to the clock pulse generator. Resurrection Summer 2019 3 SSEM — Chris Burton The Power Supply sub-system has been a little troublesome over recent months. The first issue is that the switching-on sequence relies on the operator following a defined procedure, and any deviation could result in tripping of the main circuit breaker outside the compound. It only happens rarely, but a small modification is being implemented (with curatorial permission) to reduce the risk of deviating from procedure. The second issue is that every few weeks a transient glitch on one of the power rails occurred, enough to stop a running program. This has now been tracked down to a percussion-sensitive potentiometer in one of the power modules. The same fault was noticed 14 years ago, and seemed to cure itself. But it has reappeared and appropriate action taken to fix it. Good work by the Level-4 volunteers. Our Computer Heritage — Simon Lavington Within the last few months, updates to the delivery lists of the following computers have been made: EMIDEC 1100, EMIDEC 2400, English Electric DEUCE, CTL Modular One. With the help of colleagues from the CCS-NW and from the Monash Museum of Computing History, the delivery-list of Ferranti Sirius computers is being revised. It seems that several of the Sirius machines delivered to UK customers ended their days by being passed on to Blackburn College of Technology and Design. Anyone who has first-hand experience of the Blackburn College computers, or other Sirius installations in the UK, is asked to contact Simon Lavington. IBM Museum — Peter Short Our 029 card punch has been fitted with a wooden leg. One of the back legs was damaged in transit from Oslo and the initial fix proved to be too unstable. We are now looking for a parrot to sit on top… The four punch & verifier machines on display now sit on appliance moving rollers. This means they can be easily pulled forward away from walls for access to the rear. The 029 has received a full preventive maintenance; mechanically it appears to be sound apart from one of the two drive belts that has stretched. Unfortunately we don’t have a spare but we might be OK for a while. We’ve had no success with other IBM preservation groups, however we think that a 2L23 belt is a direct equivalent. So far no replies from any belt manufacturers. 4 Resurrection Summer 2019 There were still faults in the relay circuitry somewhere; fortunately we found wiring diagrams on line and tracing continued.