When N single core processors better than one processor with N cores?

In both cases we are talking of the performance improvement due to parallelization. However, in the case of one N-core processor core can quickly share information with each other through a common(shared) cache(caches), while cores in different processors, it will take longer because of the absence of shared cache.

Based on this I was under the impression that if we have the opportunity to cram into a single processor with N cores, it is preferable to use N single-core processors. In other words, the technology of multi-core "gets" the technology of the processor and therefore the judges technology has meaning only when we are unable to push the required number of cores in a single processor.( And in this case it is better to take processors with more cores.)

Actually I'm right? Or there are still cases where N single core processors better than one processor with N cores?
July 2nd 19 at 14:07
2 answers
July 2nd 19 at 14:09
Solution
N single core processors better than one processor with N cores
when the application does not fit entirely in the caches of the processor and intensively communicates with the RAM, thus it doesn't have to intensively communicate with other instances of itself and should not refer often to someone else's memory.
the gains come at the expense of more bandwidth to the RAM.
July 2nd 19 at 14:11
1. Multi-core is cheaper than a multiprocessor system.
2. The data bus in a multiprocessor system is overloaded. Inside the multicore processor, it is more efficient.

on the other hand:

1. However, multi-core processor is more difficult to manufacture.
2. Single core processor is easier to make faster.

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