What weighs 5 tons and has less computing power than your watch? A pioneering piece of computing history call "Flossie," the last operating ICT 1301 mainframe. The National Museum of Computing recently took delivery of the dismantled computer, which needed three moving vans to bring it to the museum’s storage facility in Milton Keynes, UK.

We’re so used to thinking of computers as being so small that a perfectly practical one can fit in your trouser pocket that its easy to believe that preserving historic computers is largely a matter of finding enough shoe boxes and cupboards to put them in. However, many of the early pioneer machines weigh tons and some are so large that they’re less devices than works of architecture.

This is the problem with the ICT 1301. It has a footprint of 700 sq ft (65 sq m), weighs 5.5 tons (5 tonnes), and has a solid steel chassis strong enough to stand on without hurting it – and, believe it or not, one of its big selling points when first made was that it was small.

Roger Holmes, owner of Flossie from 1976 to 2013 (Image: bnps.co.uk)

Early mainframe computers were monsters. They weren't just large, they were gigantic. Part of the reason is that the first computers used radio valves, which were not only large glass vacuum-filled tubes that took up a lot of space, but also grew extremely hot when turned on. That means they needed a lot more space to let air circulate around them and often needed special cooling systems as well. Worse, these valves failed with depressing regularity, which required the computers to be designed to be even bigger, so technicians could get inside to replace the valves. All this made for huge, heavy machines that needed a lot of special support systems.

The ICT 1301 may seem massive by today's standards, but when it was designed in the 1960s, it was a remarkable step toward making computers smaller and more accessible because it was made using transistors instead of valves. It was one of the first mass produced computers. Over 150 were built and made up 15 percent of the machines built in the 1960s. According to the National Museum of Computing, it’s an example of second generation early British design with over 16 thousand British germanium transistors on four thousand printed circuit boards.

It was built by International Computers and Tabulators (ICT) and had a clock speed of 1 Mhz, 12 kb in the main memory and 72 kb in each of eight magnetic storage drums for a total of 576 kb. It was programmed using punch cards and non-industry standard magnetic tape. But what made the ICT 1301 stand out was that it had no valves, so no need for cooling outside of normal air conditioning, and even at five tons was small enough to fit in a business or academic building. Another plus was that it used decimal instead of binary logic, which made it easier to program, and could directly handle old pre-decimalisation pounds, shillings, and pence.

Used by insurance companies, department stores and even Britain’s Milk Marketing Board, Kevin Murrell, National Museum of Computing Trustee, says, "the ICT 1301 marks a transition from simply knowing how to build computers, to being able to install one in almost any office without needing special facilities. It had a fixed layout and all it required was enough space and reasonable air-conditioning, whereas earlier computers required special features such as false floors for cabling. The ICT 1301 was ready for work. It transformed data processing in many businesses and used punched cards, magnetic tape reels and built-in printers."

In operation, The ICT 1301 is a strange collection of clicks, whirs and worbles with magnetic tape discs lurching sporadically like the set dressing of a 1960s sci-fi epic. No doubt this was why the ICT 1301, or bits of it, appeared in a number of film and television productions over the years, including James Bond features The Man with the Golden Gun and For Your Eyes Only, the comedy The Pink Panther Strikes Again, Hammer horror film The Satanic Rites of Dracula, and episodes of the BBC science fiction adventures Doctor Who and Blakes 7.

Flossie may have been a pioneer, but its history is a precarious one, where it faced scrapping three times. Originally called Serial No 6, Flossie was delivered to the University of London's Senate House in 1962. There were five previous machines, but they were used for software development and design troubleshooting. Flossie was the first to be delivered to a customer as a working machine, so it is regarded as the first fully operational ICT 1301.

Flossie was used by the university for accounting, administration, and processing student exam results. By the early ‘70s, the computer was obsolete and in 1972 was sold at scrap value to a group of students who called themselves “Galdor” after a character from JRR Tolkien's The Lord of the Rings. Galdor leased a property in Surbiton in south west London, where they cleared the existing buildings and built an industrial shed that was barely large enough to hold the reassembled Flossie. There they worked with the aging computer for their accounting business until they needed the space for other purposes.

In 1976, Galdor sold Flossie for scrap to a buyer in Kent, who stored it in a barn on his farm along with a supply of spares that Galdor had collected over the years. The computer remained in a dismantled condition for over 25 years until the owner and a group of enthusiasts decided to restore Flossie to a working condition – a task that they managed to complete last year.

When Flossie’s owner had to sell the farm, the mainframe was offered to the National Museum of Computing, which is an independent charity situated at the famous Second World War codebreaking center at Bletchley Park in Milton Keynes and is the home of the world's largest collection of functional historic computers, including a rebuilt Colossus, the world’s first electronic computer, and the WITCH, the world's oldest working digital computer.

Rod Brown with Flossie in Kent (Image: bnps.co.uk)

Rod Brown, custodian of Flossie for the last ten years, says: "Flossie has had an extraordinary life – or more precisely, four lives. After it was decommissioned at the University of London in about 1972, it was purchased at scrap metal prices by a group of students who ran an accounting bureau for about five years. They then advertised it in Amateur Computer Club Magazine and it was bought – again at scrap metal value. After languishing for a period in a barn in Kent, it was restored with the help of the Computer Conservation Society. Visitors could then come and see, smell, and feel the vibrations of a remarkable 1960's computer. Last year, Flossie was again at risk of being scrapped, but thanks to the National Museum of Computing the machine is safe again. The team and I are delighted with this news – especially because [the museum] has such an outstanding track record of restoring computers and maintaining them in full working order. We look forward to the day that it can go back on display."

Flossie will remain in storage against a time in the near future when, space permitting, the mainframe computer will be reassembled and set to running again.

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