10 April 2016 - Bletchley Park and the National Museum of Computing

Earlier this month I visited Bletchley Park and the National Museum of Computing with my family. These are in fact two separate entities, run by two entirely separate charities. Bletchley Park is the larger of the two and has the feel of a mainstream National visitor attraction. The National Museum of Computing has a much smaller "enthusiast-run" vibe, but that is not to imply that it is in any way less significant, and is probably the more interesting of the two for someone interested specifically from the aspect of technology.

While the main Bletchley attraction is focused on the broader topic of codebreaking during World War II, of which computing technology was obviously an important aspect, the NMC is more tightly focused on the history of Computing itself. It resides within the Bletchley estate, but is set slightly apart from the main site. Possibly the main attraction within the NMC is a rebuild of the Colossus machine, often cited as the first programmable electronic computer. In fact, this really depends upon your chosen definition, but whichever way you look at it, it is without doubt of huge historic interest and absolutely fascinating.

Colossus incorporates around 1600 thermionic valves, also known as vacuum tubes. These devices are in design a bit like a modified version of an incandescent light bulb, and rely on thermionic emission of electrons from a heated element. This means they necessarily get hot, and for that reason having so many of them in one place is an engineering challenge in itself. They are a forerunner to the modern transistor, which in turn, in huge volume, forms the basis of modern computer chips. Colossus was built by Tommy Flowers, an Engineer who worked for the British Government Post Office (GPO), and one of the more unsung heroes of computing history. It was designed for the purpose of breaking the twelve-rotor Lorenz cipher machine, which was used by the German army during WWII to encrypt its teleprinter communications. The very existence of Colossus remained secret until the mid-1970s, and certain small elements of the design remain to this day subject to the UK's Official Secrets Act.

You can read more about the Colossus HERE

Possibly better known in popular culture, due in no small part to the 2014 film "The Imitation Game" starring Benedict Cumberbatch, is the electro-mechanical codebreaking machine designed by Alan Turing and known as the Bombe. The purpose of the machine was to determine the daily-changed encryption keys used by the Enigma machine, which was used by all branches of the German military and in particular by the Navy, to encode their communications. It was widely considered to be unbreakable, hence the success of The Bombe was kept highly secret, even within the British establishment, as a source of intelligence known as Ultra. Breaking Enigma, Lorenz and other ciphers is credited with having shortened WWII by two to four years. Again, due to considerations of secrecy, none of the original machines survive (we are told), having all been dismantled after the end of WWII, but the museum boasts a working reconstruction.

As well as the Colossus and Turing's Bombe, the NMC displays numerous other historical machines, including notably the Harwell Dekatron / WITCH (an acronym for Wolverhampton Instrument for Teaching Computing from Harwell). This early British computer, dating from 1951, is recognised by the Guinness Book of Records as the world's oldest original working digital computer. Its volatile memory is based on 10-state vacuum-tube counting devices known as Dekatrons. It also uses mechanical relays for sequence control, meaning it makes a fantastic noise like something from 50s sci-fi when it runs.

They also have a pair of Cray Supercomputers, one of which, the Cray-1 S/2000, is the famous circular column shape with seating around the base which housed the power supply and cooling systems. It was legendarily powerful, although the 64 bit CPU running at 80MHz sounds pretty feeble by today's standards. The vector design actually made it much more capable than those numbers might sound, but as a rough comparison it could do up to 250 megaflops, whereas the I7 processor inside the PC that I am writing this on now does 182 gigaflops, i.e. it is over 700 times as fast. The fastest modern supercomputers can achieve several hundred petaflops - i.e. at least a billion times faster than the Cray-1S. They were also legendarily expensive to buy - around 10 million US dollars at the time, equivalent to around 42 million dollars (31 million GBP) now - and also to run, consuming over 100KW, the equivalent of around 50 electric kettles running constantly. This meant it also required a complicated Freon-based cooling system. We were actually allowed to sit on the thing, making it easily the most expensive seat I have ever had !

At the less costly end, the museum also has a substantial collection of retro micros and gaming consoles, set up for visitors to play on, which makes the place fun even for those (like my kids) who may be interested more from a user's perspective.

All in all, this was a fantastic day out, and I would heartily recommend it to anyone interested in technology, computing or history.