– 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

The higher the clock speed, the more power required and the more heat generated. At a certain point it gets too difficult – nigh impossible – to cool a processor effectively in a home machine.

Instead, manufacturers make multi-core processors. This means that instead of 1 processor running at a given speed, you effectively have multiple running simultaneously at a slightly lower speed. This means that each core can focus on different tasks at the same time. Imagine you have a pile of stuff to haul away. You could throw it all into one trailer attached to a Ferrari, or multiple trailers hitched to multiple jeeps. The jeeps may be slower, but they’re working at the same time.

The reality is of course more complicated but for an ELI5, that’s the best way to look at it.

The 14900k has 24 cores. The 4790k had 4. The 14900k can effectively do 6x the work of the 4790k, and the cooling requirements are less than if you had one core running 6x faster because although each core is part of a larger CPU, the lower clock speed means they’re only going to produce so much heat each.

Edit: there are of course even more things to consider such as threads, cache size, memory, bandwidth, etc. But that will overcomplicate matters too much for this sub.