Reconstruction Colossus computer

a team led tony sale (right) reconstructed colossus mark ii @ bletchley park. here, in 2006, sale supervises breaking of enciphered message completed machine.

construction of functional rebuild of colossus mark 2 undertaken between 1993 , 2008 team led tony sale. in spite of blueprints , hardware being destroyed, surprising amount of material survived, in engineers notebooks, considerable amount of in u.s. optical tape reader might have posed biggest problem, dr. arnold lynch, original designer, able redesign own original specification. reconstruction on display, in historically correct place colossus no. 9, @ national museum of computing, in h block bletchley park in milton keynes, buckinghamshire.

in november 2007, celebrate project completion , mark start of fundraising initiative national museum of computing, cipher challenge pitted rebuilt colossus against radio amateurs worldwide in being first receive , decode 3 messages enciphered using lorenz sz42 , transmitted radio station dl0hnf in heinz nixdorf museumsforum computer museum. challenge won radio amateur joachim schüth, had prepared event , developed own signal processing , code-breaking code using ada. colossus team hampered wish use world war ii radio equipment, delaying them day because of poor reception conditions. nevertheless, victor s 1.4 ghz laptop, running own code, took less minute find settings 12 wheels. german codebreaker said: laptop digested ciphertext @ speed of 1.2 million characters per second—240 times faster colossus. if scale cpu frequency factor, equivalent clock of 5.8 mhz colossus. remarkable speed computer built in 1944.

the cipher challenge verified successful completion of rebuild project. on strength of today s performance colossus 6 decades ago , commented tony sale. delighted have produced fitting tribute people worked @ bletchley park , brainpower devised these fantastic machines broke these ciphers , shortened war many months.

front view of colossus rebuild showing, right left (1) bedstead containing message tape in continuous loop , second 1 loaded. (2) j-rack containing selection panel , plug panel. (3) k-rack large q switch panel , sloping patch panel. (4) double s-rack containing control panel and, above image of postage stamp, 5 two-line counter displays. (5) electric typewriter in front of 5 sets of 4 set total decade switches in c-rack.