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Don't you need to initialise 12 instances for the i7? It seems that you only have 50% CPU utilisation going on in that test you posted. With speeds stable at 4Ghz (still well above the 3.2 base clock rating for this processor).

I suspect that with 12 threads, the frequency will drop.

Yes, you need 12 threads in a spin loop to fully load the i7. That's why his utilization was only 50%.
 
The above screenshot from user MarkosXT states the i3 in the 2018 Mini has 2 Cores + 4 Threads.
Why doesn't report that the i3 has 4 cores ??

Yeah Cinebench shows that too. For the i5 it says 3C/6T as well. I think the program just looks at available threads and assumes the CPU is multithreaded like the i7.

Rest assured, it’s an issue with the software, not your mini. What Apple/Intel reports is correct.
 
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