19 Oct 2012
Computers that defined the information age brought back to life
Amazing how far we've come... Computers that defined the information age brought back to life | TechRepublic
Just like today's PCs the Z3 had a CPU where arithmetic was carried out, memory in which to store data, was programmable via its tape reader, and had a unit to display the output of its calculations. The other thing that that it had in common with today's computers was that it used binary to carry out its calculations - which greatly simplified the structure of its components. The memory was made up of 2,600 telephone relays - basically electromechanical switches that could represent binary 0s and 1s - that allowed it to handle 64 22-bit numbers.
The Ferranti's memory was built from cathode ray tubes (CRT) - that at the time were more commonly used by TV and radar displays. The CRT memory - known as Kilburn-Williams tube and seen here - writes information in a similar fashion to the way an old CRT TV displays a picture. It fired an electron beam at a phosphor screen to write a binary 0 or 1 - a bit - to memory. The beam alters the distribution of electrical charge on the screen and this change is detected by a metal screen or mesh that sitting alongside the tube.
Because the charge dissipates rapidly the beam had to be constantly fired to keep the bit in memory.
Of course, the memory capacity of the Ferranti was, tiny by modern standards, holding a fraction of the data of a single MP3 album track today. The machine used eight CRTs for its primary memory - each capable of storing 32 40-bit words.
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