How to do measure execution time of cpu?

I want to measure execution time of cpus and compare them like bencmark websites.

as I know we have a formula for the calculate that.

Execution time = CPI * I * 1/CR

But I stuck at the formula. I mean how do we get this data? I'm checking informations of any cpu but never encountered with them . ( specs of i7-6820EQ )

For example how to find cpi (Cycles per instruction ) ? as far as I know it is not something that can be calculated.. beside that, any manufacturer gives nothing about cpi value..

So.. How do I measure execution time of any cpu ? Is there any way to do that ? How benchmark websites doing this ?

Hasan Tıngır

Posted 2018-08-01T09:14:45.847

Reputation: 101

Why do you assume that benchmark websites have that information? – Seth – 2018-08-01T09:30:07.027

@Seth good question :) then how they compare cpus without knowing these informations ? How they decide taht which one is better proportionally – Hasan Tıngır – 2018-08-01T09:45:33.363

You run an arbitrary benchmark (the same one on each platform) and compare the numbers you get by running it against each other. – Seth – 2018-08-01T10:05:29.050

@Seth But there are thousands cpu models. I don't have enough time to do that. Instead that, culculating executing times and comparing with each other more helpful for me. (I have big data about cpu models and their specifications..) – Hasan Tıngır – 2018-08-01T10:30:30.737

But you don't have the data you require for those calculations. So just use the regular benchmark data from other sites? If you look at the definition for IPC you will find some more information about how to get it e.g. look for Dhrystone. Essentially you won't get the data you're looking for and in addition it's inaccurate. An AVX512 instruction is a single instruction that's rather complex in comparison to a simple 1+1. So for a given timeframe a CPU just doing 1+1 will have a higher IPC which is useless if you're using AVX.

– Seth – 2018-08-01T10:45:13.163

Answers

If you are looking for comparing CPU models, your best source of information is the website of PassMark Software, advertised as :

1,000,000+ Systems Tested and 3,100+ CPU Models - Updated Daily!

PassMark Software have their own benchmarks for testing all the components of computers including CPU, disk, video and RAM, which are run by volunteers and then integrated into the overall statistics.

harrymc

Posted 2018-08-01T09:14:45.847

Reputation: 306 093

The comparison of CPU is a complicated work. First of all you should understand that there are different classes of calculations and CPU executes them in a different manner. Depending on it you CPI would be different for one CPU. In some cases it is difficult to count the I parameter (for example for speculative instructions). Also your formula does not take into account data and instruction stalls.

In my opinion one of the best benchmark set is SPEC. For CPU it is divided onto two problem sets: FP (Floating Point) and INT (Integer). Each set has different tasks that show the CPU performance in different cases. This bencmark counts the time (yes, just the clock time) to execute each task and then you can compare different CPUs and see which is better for concrete case (the time is preliminary normalized).

alexanius

Posted 2018-08-01T09:14:45.847

Reputation: 11