What factors determine the choice of time allocated for one cycle of the microprocessor?

Question

Electronics

Hello. I'm preparing for my exam. Question: What factors determine the choice of time allocated for one cycle of the microprocessor?
Rummaged through all lectures - there is no answer. Help me please. You can even without going into deep details. I do not think that they will strictly ask, but you must be ready to answer at least something.

Answer 1

The switching speed of transistors, which is determined by the CMOS technology with which the chip is made.

Answer 2

If we were talking about simple digital (logical) microcircuits, then in them the tact time is set by their speed, in a pure, uncomplicated form. Well, i.e. Literally - if the cycle is reduced (increase the clock frequency), then the number of failures due to the overlapping of the pulse fronts on each other from a certain value will increase beyond the allowable. After all, the duration of the rises / falls cannot be changed (it is set by technology), and when the duration of the clock pulses is reduced, they cease to look like pulses and approach a sinusoid in shape - the rectangular shape is smeared.
In processors, all this is exacerbated by a bunch of cross-connections and a bus structure. Let's say you need to transfer a transition from 00000000 to 111111111 over an 8-bit bus, say, from the ALU to some register. If the signal is late on one of the lines - you will get a transmission error. In order not to be late, the takt time will have to be increased, i.e. create sufficient margin to compensate for such propagation delays. This is how it is chosen. To reduce it (i.e., increase the processor speed), the bus must be strictly symmetrical in terms of the signal propagation time.
But there is a bonus: the length of the conductors and their parasitic capacitances on the processor chip are minimal. This is what made it possible to reach the current gigahertz, which were unimaginable just 20 years ago.

Answer 3

Some vague question. Takt time is inversely proportional to frequency, obviously. The frequency depends on the manufacturing technology of the processor and its design (if you go into details, then on the length of the critical path in the design). But what the one who thought up such questions had in mind was that one must be a telepath.

Answer 4

I will add my mite (five kopecks).
The clock frequency is chosen - the maximum at which the transistor circuits have time to work. This means that the designer plans to work something like this:
"Here, voltages corresponding to the input data are applied to the input of this circuit; these voltages are within the limits of the standard (for example, TTL or whatever it is). I plan that I will need the result of the calculations in three cycle. With this design, this circuit will complete all transients and set the voltage within the standard for such and such a time. So, three cycles should cover this time in excess."
Transients basically consist in the fact that it is necessary to charge the parasitic capacitance (existing between any wires); and until you fill in the right amount of electricity there, the voltage there will be incorrect (not corresponding to the standard).
And the speed of pouring electricity is determined by the resistance of the wires (the voltage is considered fixed - according to the standard).