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I am currently working on a comparison between several single-board microcontrollers and I am trying to compare them according to several aspects (CPU, RAM, Price and features).

When it comes to CPUs, it gets a bit more tricky as some boards have 1 core and others are Quad-Core.

How can I compare CPUs given CPU frequency and the number of cores?

More precisely, how can I show, in a proper way, that a 1.7 GHz single core is better/worse than a 1.4 GHz Quad-core?

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closed as too broad by Keltari, James, Ƭᴇcʜιᴇ007, Tog, Breakthrough May 27 at 22:29

There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.If this question can be reworded to fit the rules in the help center, please edit the question.

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Do what CPU Boss does since they already do this... They do single core vs single core, multi vs multi. Any way, your question is, IMO, off topic here (Sorry) –  Dave May 27 at 14:13
    
Oh, is it OT? Sorry, I saw some other similar questions behind asked and answered and I thought it was the right place. –  N3sh May 27 at 14:15
    
I said I think it is, doesn't mean it is! :) Any way, I removed the last sentence, I think it's on topic now :) BUT, you need to clarify what you mean by 'better'. Lower voltage? Easier to overclock? –  Dave May 27 at 14:16
    
Alright, thanks! :D –  N3sh May 27 at 14:18
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Comparing CPUs with more than one factor is apples and oranges. It all depends on usage. –  Keltari May 27 at 14:21

2 Answers 2

up vote 1 down vote accepted

There's not perfect answer to this question but I can try to give you some guidelines on how to choose. What CPU is best really depends on the type of software you are trying to run on it. If it has been written to run perfectly in parallel the quad core processor will be better because it can use all 4 cores at the same time to run computations. If the software is not written to run in parallel (all of your computations must be run one after another) the single core processor will run it better because it has a higher clock rate.

If your software is perfectly optimized to run in parallel you can calculate how many instructions per second your microcontroller can calculate using

number_of_cores * frequency_of_computations = instructions_per_second

For the two examples you listed above in the case that the software can be run perfectly in parallel

Single Core 1.7Ghz

1 core * 1.7 GHz = 1.7 billion instructions per second

Quad Core 1.4 Ghz

4 cores * 1.4 GHz = 5.6 billion instructions per second

But if the software must be run in sequential order then the number of intructions you can run per second is simply the clock frequency

For the two examples above in the case that the instrcuction must be run in sequential order

Single Core 1.7GHz

1.7 billion instructions per second

Quad core 1.4 GHz

1.4 billion instructions per second

As you can see, depending on the software running on the system, either microcontroller could be the better one. This is where you, as a designer have to make a decision. You have to ask yourself: How will the software interact with the hardware? Based on your answer to this question you will need to make a decision on which type of hardware you'd like to use.

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You cannot. CPUs' efficiencies vary widely.

A direct comparison is only possible with other CPUs of the exact same architecture.

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