How much power did the collussus have in comparison to todays technology?

Answer 1

It is hard to put a figure on it because, although both the Colossus and modern computers are universal Turing machines, the fundamental nature of their designs are very different.

The common crude way to compare the 'power' of modern processors is by how many floating point (FLOPS) or integer (MIPS) calculations can be performed per second. Since the colossus did not have dedicated arithmetic units in the way we think of them now, these measures are inappropriate.

Considering system clock speed, the (mark II) Colossus' clock was generated by the paper tape reader to keep the machine synchronised with its paper-tape program. The clock speed was, therefore, limited by the mechanics of the spooler and the integrity of the paper. The safe limit used was 5000 characters per second (which may crudely be thought of as 5KHz). Since modern computers operate at around 3GHz, we can crudely say that this is six-hundred-thousand times faster. However this hides the fact that a modern general-purpose processor is vastly more flexible in its abilities and so can perform certain operations with just a few clock cycles that may have required huge programs to calculate on the Colossus.

Conversely, however, the Colossus was designed to perform a very specific function, and so could do that very efficiently. In evidence of this, Joachim Schüth wrote a decrypt code in 2007 that could crack the enigma code running on a 1.4GHz laptop. Comparing the speed of calculation to that of Colossus, he stated: "My laptop digested ciphertext at a speed of 1.2 million characters per second-240 times faster than Colossus. If you scale the CPU frequency by that factor, you get an equivalent clock of 5.8 MHz for Colossus. That is a remarkable speed for a computer built in 1944."