The Z3 is a clocked machine. Konrad Zuse used this principle to synchronize the different components of the machine. In order to do this he implemented a special impuls generator with a drum. The impuls generator stepwise provides the different relay groups with electrical power. The clock frequency was around 5.3 Hertz depending on the quality of the telephone relays, so the faster the clock then the faster the machine. Konrad Zuse mentioned that a multiplication of two floating point numbers took about three seconds. The Z3 needed 16 cycles for a multiplication. For this reason the clock frequency is 16 / 3 » 5.3 Hertz. In order to avoid sparking of the relay contacts when switching them, he used the drum to drop off the electricity at the switching time. This principle avoided material rust and guaranteed a long functionality of the relay contacts.
Micro Sequencer and Pipelining: The heart of the control unit of the Z3 are the micro sequencers. Every cycle in the Z3 was divided in five steps I to V. The steps IV and V are used to transfer information from one part of the Z3 to another one, for example the contents of a register to a memory cell. During the steps I II and III an addition or subtraction in both parts of the arithmetic unit is executed. This is the execution phase of an instruction. A typical instruction takes the arguments of the operation, executes an operation and writes the result back. Konrad Zuse considered it as very important to save execution time, that he executed the instruction in an overlapping way (See the picture). It is kind of a pipelining principle.
It is not well known, that Konrad Zuse in 1949 applied for a patent for a pipelining computer in 1949.
At June 30, 1949 Konrad Zuse applied for a patent of the first pipeline computer of the world and got it as late as on December 6, 1962. The title of the patent is: Rechenmaschine zur Durchführung arithmetischer Rechenoperationen (z.B. Multiplikationen. Translation: Calculator for the execution of arithmetic operations, for example multiplication). It was a machine consisting of eight independent arithmetic units which could execute partial arithmetic operations on certain data. With this machine it was possible to execute arithmetic operations for a large set of data.
We now are coming back to the micro-sequencers of the Z3.