– Why does clock speed matter on a CPU, and why do some top-tier CPU’s have lower clock speeds than some from nearly 10 generations ago?

Question

I have a good understanding of what clock speed is, but why does it matter?

For the second question, I was wondering since for example, the new i9-14900K has a base clock speed of 3.2 GHz, whereas my previous desktop CPU, the i7-4790K, had a base clock speed of 4.0 GHz. Why hasn’t this number steadily gone up thought the years?

In: Technology

Answer 1

Clock speed does matter for otherwise equal chips as the one with a higher clock rate will do more work for a given cycle.

Now there are so many factors besides clock rate that improve/degrade performance of a chip.

Ultimately the things that you really want to look at are how a given chip will perform for a specific task.

Doing a bunch of scientific computation? You want high FLOPs (floating point operations per second).

At the end of the day, focusing on the output a chip can produce matters more than simple stuff like clock rate and the like.
For example: If I, a hypothetical chip architect company, wanted to make a chip with a 10 GHZ clock, I could. The approach would be to add many pipeline stages (which in effect splits the entire processing of a piece of code/instruction into multiple steps). There are many unintended side effects of doing this (branch misses being top of mind currently), but I could happily and accurately advertise a 10 GHZ cpu.

All this is to say that computer architecture is an immensely fascinating field and this question asked gets at the core of engineering, balancing tradeoffs in design and implementation of engineered products.

Edit: I want to note that the explanation above is mostly true, but contains simplification/untruths made for convenience of explanation.

Edit part 2, the sequel: I didn’t realize this was ELI5. The ELI5 explanation can be summed up as “Clock rate is only part of the story of what makes a CPU fast.”