Manchester Mark I: Tommy Thomas with the prototype drum

• G. E. (Tommy) Thomas with the second prototype magnetic drum store which he developed for his MSc project, to be used on the Manchester Mark I. The first prototype was constructed in the department and worked sufficiently well to transfer complete pages between the drum and CRT stores. The second proptotype (shown) was built by Ferranti engineers J. Dean and R.D. Evans to tighter tolerances. The drum store was subsequently product engineered by Ferranti for the Ferranti Mark I - shown in $set206, the Ferranti Mark I drum being taller than the 2" high prototype providing more tracks, ie more pages of drum store.
  
• Manchester code, originally "Phase Modulation", was invented by F.C. Williams for the prototype drum store and was subsequently widely used as a magnetic tape standard for 1600 bpi tape, and more widely used in digital communications.
  In his Digital Pioneer Computer lecture in 1981 Dai Edwards, a contemporary MSc student of Williams, said "F.C. came up with the phase modulation system" (time 37' 30").
  
• The Manchester Mark I was shut down a few months before the Ferranti Mark I was delivered. The Manchester Mark I's drum store was then used as the main memory of the transistor computer $set316. Dick Grimsdale explained in his talk to the Computer Conservation Society (North West) in Manchester that Williams Tubes were a bit of an anathema for a transistor computer because "they had nasty high voltages and after all they were valves", and he couldn't get hold of any Williams tubes anyway so that settled it. There happened to be "a rather old drum" available from the prototype Mark I (the Manchester Mark I) and so he used that. The drum shown in this image was therefore used in two breakthroughs: the invention of Manchester Code and the first transistor computer.
  
• Other views of the drum store are $set205 and page107a. In page107a there is a different head block to the one published at the time - see IMG5038, which was presumably a prototype while page107a appears to show a more engineered head block, perhaps being tested for use in the Ferranti drum.
  
• Gordon Eric (Tommy) Thomas, 1928-2024 passed away on 3rd July 2024. Simon Lavington wrote a brief obituary for the Computer Conservation Society's Ressurrection magazine (Spring 2025):
  Tommy Thomas was born in Carmarthenshire and went to Manchester University where he graduated with first class honours in Physics and Electronics in 1948. He then joined the expanded Baby computer team as F C Williams' research student. Working with another researcher, Cliff West, Tommy's task was the implementation of a magnetic drum backing store. This store had three innovative features. Firstly, information was transferred between RAM and drum in convenient chunks called pages. Secondly the drum was synchronised to the central computer's clock, thus allowing for multiple drums. Thirdly it used a novel data-encoding scheme called Phase Modulation, later known as Manchester Code. Manchester Code became a standard for magnetic tapes and floppy disks and was widely used in digital communications, including the Voyager spacecraft and early Ethernet networks. It is still used in many domestic remote controllers. Once the prototype Manchester computer had been re-engineered as the commercially-available Ferranti Mark I, Tommy helped to design a faster successor named Meg, which first ran a program in 1954. This became the Ferranti Mercury. Tommy left the University in 1955 to lead a new Central Digital Computing facility at Imperial Chemical Industries Ltd. In 1966, following the UK government's decision to set up three major Regional Computing Centres, Tommy moved to Scotland to head the Edinburgh Regional Computing Centre - (the other Centres were at Manchester and London). In 1985 Tommy moved to Australia to lead the Commonwealth Scientific and Industrial Research Organisation's new Division of Information Technology. The Division's role was to identify opportunities for the development and exploitation of Information Technology. In 1988 Tommy was seconded to assist in the organisation of Bond University, the first private university in Australia. He became the Foundation Professor of Computing Science. Tommy retired in October 1990 to pursue voluntary work in the community.
• In Hilary Kahn's catalogue of documents and images (c2006) the title for this image is "Early Drum and GET June 1949 (Daily Express)" and the notes state "On reverse: 49-3148. Daily Express (Copyright Photograph) Gt. Ancoats Street, Manchester" if the copyright was held by the Daily Express then the photograph is over 70 years old and copyright has expired.

---

This is the best of set $set412, which contains images P4139J18-HJK16-4A and P4286J8-HJK22-12A. ID: P4286J8-HJK22-12A. 7106x4960 (+TIFF) . Copyright: unknown. Collection: Scans of prints in Hilary Kahn’s original Departmental archive. Source artefact: P4286J8-HJK22-12A, 6" x 4" photographic print, condition: Fine. Artefact notes: On reverse: 49-3148. Daily Express (Copyright Photograph) Gt. Ancoats Street, Manchester.

---

Set edited 27-Aug-2025 (Jim Miles)

---