– 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

Inside of the CPU is a bit of quartz crystal. These crystals have special property that allows them to vibrate at specific speeds when electricity is applied. Those vibrations can be used to control electricity passing through different parts of the CPU with extremely precise timing.

Let’s say you press the “K” button on your keyboard. The keyboard needs to send pulses of electricity to the CPU so that it can make the letter appear on your screen. These pulses have either “High” voltage or “Low” voltage. These highs and lows are often displayed in binary as 1s and 0s. The binary code for the letter K is “01001011”

So, imagine a single pin on the CPU is used to input keyboard commands. The CPU has to read the voltage on this pin 8 times to determine the letter. That’s where the quartz timing comes in. It controls how often the CPU will check this pin and read either a 0 or a 1 based on the voltage. Higher rates of pulsing allow the CPU to read all 8 values faster.

Each time the clock pulses, all the pins on the CPU is read, and electricity will move around the inside of the CPU through billions of little transistors. Electricity doesn’t like moving around and actively resists it. You can think of this like friction from moving inside the wires. That friction causes everything to heat up and too much heat will melt or burn out parts.

So to recap, the clock speed is important because it controls how frequently voltage values are sent to and received from the CPU, and therefore how quickly the CPU can perform tasks. It also controls how quickly heat is generated from moving those voltages.

Modern day CPUs have additional resources to allow them to perform certain tasks much more efficiently and can accomplish some tasks faster, even with a slower clock speed. In addition, modern CPUs are really multiple CPU cores combined into a single package. Each core can work on a different task simultaneously, making everything faster. It’s like cloning yourself 3 times. It’d only take you 2 hours to finish your work day instead of 8!

Because of these modern efficiencies, CPUs can operate with less electricity, and slower clock speeds and still complete tasks much faster than older models.