How is Processor Speed Measured?

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There was a time when how well a processor performed was judged by its clock speed primarily. However, today, the clock speed has been relegated to being just one of many metrics that goes into determining a CPU speed. This begs the question, how is processor speed measured exactly?

For a consumer, the best way to measure the speed and to understand how fast your processor is is to use popular benchmarks.

In reality, there isn’t a standard meter scale or a yard stick with which we can measure something so complex as the speed of a processor.

Everything including the clock speed, number of cores, number of threads, transistor size, its architecture etc contribute to a CPUs performance as a whole. However, we do have very popular and trusted BENCHMARKS which can give us a good insight into how fast a certain processor is.

Some popular benchmarks include, but not limited to:

  • Passmark
  • Cinebench R15
  • Cinebench R20
  • Cinebench R23

It is a common belief now that looking at clock speed alone to measure the speed of a CPU is a myopic and an outdated way of judging a CPU’s performance.

So How is Processor Speed Measured?

As mentioned earlier, there are various characteristics that define the speed of a processor as a whole.

But for you as a consumer the simple answer to the question how the processor speed measured is through popular benchmarks. 

Use Benchmarks to Save Yourself from the Headache

If you want to save yourself from the headache of understanding what clock speed is, what instructions per second is, what the CPU architecture design is etc, then just look at the scores of a given CPU on popular benchmarks.

As mentioned earlier, there are many popular benchmarks out there including but not limited to Passmark, Cinebench R23, R20, R15.

  • Passmark Benchmark – This is a very popular benchmark for understanding how the CPU performs overall
  • Cinebench R15, R20, R23 – This is also a very popular benchmark. With each iteration it adds newer insights into the CPU performance

Single Core and Multi Core Performance

When understanding the speed of a CPU, you have to look at both its single core as well as its multi core performance.

Cinebench is an excellent benchmark for measuring the CPU’s single core and multi core performance separately.

What is Single Core Performance?

Cinebench r20 i5 vs i7 for video editing 3
Single Core performance of flagship 9th, 10th, 11th, 12th Core i5s and i7s. 

The single core performance of a CPU is, well, how well a single core performs with the rest turned off.

This is a very important measure as most tasks in software or games are still heavily single core based.

If each core is a worker, then single core performance defines how much muscle each worker has to lift things.

CPU lines in the same generation are often similar in terms of single core performance.

For instance 11th Gen “K” series i5 and i7 have almost the same Single Core Performance. Similarly, 12th Gen “K” series i5 and i7s have almost the same single core performance as can be seen in the chart above.

What is Multi Core Performance?

Cinebench r20 i5 vs i7 for video editing multicore 2
Multi Core performance of flagship 9th, 10th, 11th, 12th Core i5s and i7s. The higher the number of core, the better is the multi-core performance naturally.

The multi core performance of a CPU defines how well a CPU performs with all of its cores working simultaneously.

Having more cores means your CPU can multi-task more effectively.

However, having a lot of cores on a CPU can be a double-edged sword. If the tasks that you perform, the software you use, or the games you play do not utilize the number of cores your CPU has, then you will not see any performance gains.

For instance, most games scale well upto 6 cores, but any thing beyond this number gives minimum benefit. Hence Intel Core i5 or AMD Ryzen 5 are often recommended for gaming.

Also Read: How Many Cores Does an i5 Have?

Rendering and encoding, on the other hand, eat up core count, hence Intel Core i7 and Ryzen 7 are often recommended for video editing and streamers.

Also Read: How to Check What CPU You Have?

Is Clock Speed A Measure of CPU’s Speed?

Clock speed is still considered by many to the most important measure of how fast a CPU is. While this is a very important characteristic for measuring the speed of a CPU, it is NOT the only one.

Take for instance, the 11th Gen Intel Core i7 11700K and the subsequent 12th Gen Intel Core i7 12700K, despite both of them having 5.0 GHz clock speed, the latter is significantly more powerful. 

Cinebench R23 Single Core Score : Core i7 11700K vs 12700K

i7 11700K vs 12700K single core R23
Source: CPU-Monkey.com

Cinebench R23 Multi Core Score: Core i7 11700K vs 12700K

i7 11700K vs 12700K multi core R23
Source: CPU-Monkey.com

Clock speed these days ONLY matters if you are comparing CPUs in a given generation.

Meaning if you compare CPU within, say, Intel 11th gen or Ryzen 5000 series, then yes, clock speed would have a direct impact on performance.

But a cross-generation analysis based solely on clock speed would be unfruitful.

Also Read: What is CPU Throttling?

What is the CPU Clock Anyways?

The CPU and all the components inside it need to be synchronized in order to work correctly.

CPU being the orchestrator demands that all the components follow its lead precisely when it says so.

To achieve this, the processor makes use of an internal oscillator (aka internal clock) that tells the different components when to work.

The speed of the oscillator is what is more commonly referred to as the clock speed of the processor and it defines how many cycles (On/Off) the clock goes through in a second.

The higher the clock speed, the faster the instructions can be passed to and from the components.

Clock speed is given in frequency Hz, MHz or GHz, which basically defines how many times the clock turns ON/OFF or cycles in a second. a 1 MHz clock cycles only one time a second. A 1 GHz CPU can cycle 1,000,000,000 times a second.  

Also Read: What is a Good Processor Speed for a Laptop?

Staircase Analogy

A good analogy here would be the steps on a staircase. Clock speed defines how many steps a CPU can climb in a second.

Higher the Clock Speed, the more steps a CPU can climb.

How is Processor Speed Measured
A rudimentary analogy. Higher the clock speed the more steps a CPU can climb in a second. 

What About Instructions Per Cycle – Is IPC a Good Measure of CPU Speed?

Instructions per Cycle or IPC is a better indicator of CPU’s speed compared to Clock Speed alone.

IPC and clock speed are both very closely related characteristics of a CPU.

All CPUs follow an instructions set. An instruction set is essentially a catalog of all the commands a CPU can give and execute. This is built into the CPU itself intrinsically and it is part of the CPU’s design architecture.

When you perform even the smallest of tasks such as copying and pasting a file. The CPU executes a series of instructions.

How fast a CPU executes instruction in a given time (often a second) is referred to as instructions per cycle or IPC. 

Clock speed by itself does not mean much if the CPU isn’t executing instructions.

This is similar in analogy to a water pump. If a water pump is running very fast but it isn’t pumping any water then how quickly it pumps doesn’t mean much. 

instructions per cycle IPC
Not all instructions are the same. Some take longer time (clock cycles) to execute. Similarly not all CPUs are the same. Some take fewer clock cycles to execute the same instruction.

Another point to note is that certain instructions take fewer while others take a lot of clock cycles to get executed.

This also closely relates to how the CPU is designed (Architecture). A good CPU design would execute a certain instruction in fewer clock cycles. Whereas a bad CPU design would require a higher number of clock cycle to execute the same instruction.

Therefore, while the instructions can be the same across generation and models, the way they are designed and how those instructions are executed vary from CPU to CPU.

Hence, again, clock speed is NOT the primary measure of how fast a CPU is.

Again taking the analogy of a water pump, the clock speed is analogous to how fast the rotor of a water pump rotates. How fast a rotor rotates does not indicate how much volume of water (instructions) it can pump with each rotation. Some can pump little while others can pump huge volume per rotation.

It is for this reason that despite both Intel Core i7 11700K and Intel Core i7 12700K having the same 5.0 GHz clockspeed, the 12th Gen Core i7 12700K is much more powerful than the 11th Gen counterpart.

AMD IPC Improvement Made Them Popular

There was a time when AMD competed with Intel CPUs in terms of their clock speed. However, AMD with their release of Ryzen CPUs have long ditched that competition and has instead turned their focus on improving their IPC.

AMD still does not reach the clock speeds of Intel counterparts, but their IPC keeps improving with the each iteration of their Zen architecture. 

As such, AMD’s new architecture have been aiming to execute higher instructions at a slower clock speed (compared to Intel).

Is IPC the New Measure of How Fast a CPU is?

Unfortunately no. It is a good measure, but judging a CPU’s speed by IPC alone can also be misleading. Why? because a bias can arise here.

How good a CPU performs in terms of IPC depends upon which software you have benchmarked it on.

Certain CPUs can fetch-decode-execute instructions of a certain program in fewer clock cycles, whereas, they may perform worse in others.

Therefore, IPC benchmark of a CPU is often an average score. It does NOT define how the CPU will perform in various scenarios.

One such case is gaming. Game engines have essentially been designed with Intel’s architecture to leverage a CPU with a higher clock speed. 

The following video explains this. (You don’t have to watch the entire video, just the first 6-7 minutes would give you good insight).  

CPU Generations – Architecture – Transistor – Cache Size All Matter 

So in the end, measuring the processor speed is not just about looking at either the clockspeed or IPC. Their myriad of other factors that define how processor speed is measured.

With each new generation, CPU brings a drastic improvement in their architecture and performance.

Newer generations also reduce the size of the transistors. Smaller transistors mean denser chips which equals higher computation. After all, a CPU is nothing but an arrangement of microscopic transistors.

Cache memory is another characteristic that defines how fast a processor is. While this isn’t generally considered a very important a characteristic by consumers, a larger cache memory means the CPU can access instructions faster. 

Multiple Cores – Multiple Threads and CPU Performance

Intel Core i7 4770K dye chart
Intel Core i7-4770K dye chart showing four cores.

The amount of cores a CPU has goes hand in hand with how processor speed is measured. 

Each core is basically a CPU in itself meaning it has all the sub components of what a typical CPU would have such ALU, registers cache etc.

You can consider each core as a worker. The more workers a CPU has, the more tasks it can handle simultaneously

Hence, the higher number of cores often means better performance, particularly with multitasking or when using a software that can run tasks simultaneously.

Multicore processors are not a new phenomenon as most computer CPUs have at least two cores. 

However, having a CPU with a high number of cores would ONLY make a difference, if the tasks that you perform or the software you use or the game you play actually utilizes all of its cores well.

If you have an 8 core processor, but if the tasks that you perform or the game that you play can only utilize a maximum of 4 cores optimally, then you will not experience the true prowess of an 8 core processor.

Hence we have separate benchmarks for single-core and multiple-core performance scores for a CPU.

Also Read:

Conclusion

So the answer to question “how is processor speed measured” is complex. If you judge a CPU’s speed by it specifications alone, then it will be very difficult to put a particular score to it.

Hence, we, as consumers, use benchmarks such as Passmark and Cinebench to give us an insight into the performance of a CPU and how it compares with the rest.

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Atif Qazi
Atif Qazi is the founder of PCGuide101. He is a digital nomad who loves everything PC. He is a PC builder, tech enthusiast, engineer, and a lover of single player lore-rich RPG games.

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