Bletchley museum treasures vintage tech

Bletchley museum treasures vintage tech

Summary: ZDNet UK took advantage of a recent visit to Bletchley Park to uncover some of the thousands of items of IT heritage that the National Museum of Computing has in store

TOPICS: After Hours

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  • Bubble memory

    Bubble memory
    For a couple of years in the mid-1970s, bubble memory seemed to be the way ahead. It works by shuffling tiny magnetic domains around a sheet of orthoferrite — an iron/rare earth/oxygen compound — by putting current through the sheet. It was denser than other memory systems, very robust, reasonably low-power and cost-effective. The bubble memory shown here is Intel's 7110, a 1Mb device, that saw use in a few laptops and embedded systems in the early 1980s. The unit here was made in 1984, towards the end of the technology's relevance.

    Ordinary solid-state memory developed faster than bubble memory and soon saw it off; it was always much faster, but soon became denser, cheaper and lower-power. 

    Photo credit: Rupert Goodwins

  • Ferranti Pegasus Delay Line Memory

    Ferranti Pegasus Delay Line Memory
    Hailing from around 1957 and using three valves, this unit from the British designed and built Ferranti Pegasus computer stores the equivalent of five bytes of data in a long nickel delay line that's coiled up below the paxolin panel seen here. The Pegasus actually used 40-bit words as its basic unit of data, one of which could be stored here. The line worked through data being fed in at one end by the equivalent of a speaker, and taken out again on the other end after it had spent some time travelling along the delay line as sound waves.

    The designer of the delay line, John Fairclough, was a junior engineer at the time: he finished his career as Sir John Fairclough, chief scientific adviser to Margaret Thatcher.

    Photo credit: Rupert Goodwins

  • Ferrite core memory

    Ferrite core memory
    Invented in 1955, ferrite core memory was the mainstay random access storage medium for mainframe and minicomputers throughout the sixties. It works by hundreds or thousands of tiny O-shaped ferrite rings — ferrite being a iron-containing ceramic — that can be magnetised when current passes through two wires threaded through their centre.

    This magnetism can be read back by another wire — the sense wire, which also passes through the core. However, to get this signal, the ferrite has to be demagnetised by a pulse of electricity through the first wires. Thus, once read, the ferrite has to be reset back to its original state. Density is low, with one bit per ferrite, but planes of core memory.

    When not being read, however, ferrites were non-volatile; you could switch a computer off overnight and turn it back on with memory contents intact. The first solid-state memory replacements for core store had huge batteries to try and replicate this behaviour, until it was realised that reloading off tape was almost always more sensible.

    Photo credit: Rupert Goodwins

Topic: After Hours

Rupert Goodwins

About Rupert Goodwins

Rupert started off as a nerdy lad expecting to be an electronics engineer, but having tried it for a while discovered that journalism was more fun. He ended up on PC Magazine in the early '90s, before that evolved into ZDNet UK - and Rupert evolved with them into an online journalist.

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  • Always pleased to see news about Bletchley. I was going to visit (again) this holiday period but the weather was too good!