If you have ever done much comparison shopping for a new CPU, you may have noticed that cores all seem to have the speed rather than a combination of different ones. Why is that? Today’s SuperUser Q&A post has the answer to a curious reader’s question.
Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.
The Question
SuperUser reader Jamie wants to know why CPU cores all have the same speed instead of different ones:
In general, if you are buying a new computer, you would determine which processor to buy based on the expected workload for the computer. Performance in video games tends to be determined by single core speed, whereas applications like video editing are determined by the number of cores. In terms of what is available on the market, all CPUs seem to have roughly the same speed with the main differences being more threads or more cores.
For example:
- Intel Core i5-7600K, base frequency 3.80 GHz, 4 cores, 4 threads
- Intel Core i7-7700K, base frequency 4.20 GHz, 4 cores, 8 threads
- AMD Ryzen 5 1600X, base frequency 3.60 GHz, 6 cores, 12 threads
- AMD Ryzen 7 1800X, base frequency 3.60 GHz, 8 cores, 16 threads
Why do we see this pattern of increasing cores, yet all cores having the same clock speed? Why are there no variants with differing clock speeds? For example, two “big” cores and lots of small cores.
Instead of, say, four cores at 4.
0 GHz (i.e. 4×4 GHz, 16 GHz maximum), how about a CPU with two cores running at 4.0 GHz and four cores running at 2.0 GHz (i.e. 2×4.0 GHz + 4×2.0 GHz, 16 GHz maximum)? Would the second option be as equally good at single threaded workloads, but potentially better at multi-threaded workloads?I ask this as a general question and not specifically with regard to the CPUs listed above or about any one specific workload. I am just curious as to why the pattern is what it is.
Why do CPU cores all have the same speed instead of different ones?
The Answer
SuperUser contributor bwDraco has the answer for us:
This is known as heterogeneous multi-processing (HMP) and is widely adopted by mobile devices. In ARM-based devices which implement big.LITTLE, the processor contains cores…
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