Processors / cores?

In one form or another, the issue was raised in different places, but usually it becomes a broad discussion about smart or beautiful. Try to formulate the question clearly.


What computer configuration will give more performance: one processor on the 2N cores or processors Douma on N cores, provided that the other parameters are the same? Why? If different applications the result is different, for what and why?..


The question was born from the announcement of the new Mac Pro. It will be a single processor, but it will have 12 cores (including HT or not — I don't know). Many MacOS users disappointed. Better if it will be demanding for the CPU applications, or worse than if it had two CPU 6 cores?
October 3rd 19 at 02:46
6 answers
October 3rd 19 at 02:48
Communication between cores is faster than between processors. 2 different CPU tasks(one for each) that does not overlap will be faster than 2 cores with the same conditions. Because cores shared cache and the processors exclusive. If the scheduler would be good to assign tasks, then, theoretically, a lot of CPUs with fewer cores will be more efficient.

This is all my personal opinion, because no real tests I did.
Ie for multithreaded applications better to more cores on a single chip, and for many a lot better single-threaded cores on different chips? How realistic is it using an internal cache of the chip (by the way, he shared or common?) for data exchange between threads on neighboring cores? The streams generally "know" that they are executed within the same chip or on different? - arnoldo98 commented on October 3rd 19 at 02:51
no, it's all in the scheduler, it is his job to distribute the threads across the cores\processors. Process, as such, it represents a set of threads. But for a thread\process, you can request to be executed on a specific CPU(CPU affinity), i.e. to manually control its determination to the CPU. In this regard, it is possible to vary the flows in different ways and to different performance. But, I believe that the CPU affinity is more for server software and the Mac OS on "personalka" nothing to do with it.

How realistic is it using an internal cache of the chip (by the way, he shared or common?) for data exchange between threads on neighboring cores?

As a rule, in modern custom CPU level 3 CACHE. All of them are used within a single crystal is very intense. More better to read yourself, too big topic. Well it is described by its Tanenbaum Structured Computer Organization.

The streams generally "know" that they are executed within the same chip or on different?

Don't know exactly, but it is likely that this information can be obtained. "Default" is should not worry, the programming more towards task-based, which removes the developer from even flow, pure and simple.

In General howling about the lack of 2 crystals, I think, is fans of gigahertz and gigabytes. Who know little of modern(and perhaps all) of the gland. - Ashlynn commented on October 3rd 19 at 02:54
October 3rd 19 at 02:50
Yeah no particular difference, and two and four percent of the bet to double or quadruple the number of cores, and not instead of the four nuclear percent to put two percent two cores and increase performance.
Marketing — 100%. 2 at 4 4 at 2 — still sooner or later the first "bump" in the disk drives and memory. - arnoldo98 commented on October 3rd 19 at 02:53
October 3rd 19 at 02:52
The question is incorrect and is not about that.

If we have two identical nuclei, and the difference — if they sit on a single chip or on two different boils down to the problems of heat dissipation and cooling.

However, if you leave the total the same cache, but to make it shareable between cores, then there is the expense this one is a win. (actually, this is done at Intel).

But the essence of the question. I assume that MacOS users are disappointed that instead of increasing the power of one core increased their number. However, not all tasks are well rasparallelivanija and not all capable of extremely at the moment, to use all 12 cores
The MacOS users, I guess, disappointed that "of such processors could be 2!" And that to increase the power of a single core, then the MacOS users probably realize that this is a question for Intel, not Apple. But Apple decided that the system will be only one processor, without the possibility of extension. - arnoldo98 commented on October 3rd 19 at 02:55
I don't follow Apple products, but I somehow think that the possibility of upgrading from the Mac-books have always been limited. And therefore it cannot be a disorder. And two ovens at 90 watts each — it's still the same problem in their cooling in a small and cramped case. This is what I? — To what. it does not say waiting two processor in the MacBook looks very strange. - Ashlynn commented on October 3rd 19 at 02:58
And where does the MacBook? We also talked about the Mac Pro. - torrey11 commented on October 3rd 19 at 03:01
Hmm, and why do I think about Macbook? Well then, Yes — waiting looks more logical. - arnoldo98 commented on October 3rd 19 at 03:04
October 3rd 19 at 02:54
if 2 processors will be, they will be probably easier to cool, each of them will be less warm than one with 2N cores
Question about performance and not about working conditions. I not so well understand the architecture, to say that would be an obvious gain in one level or another. Caches of cores and chips, buses, memory channels, etc. — it's not so simple to arrange. For what applications is the bottleneck? - arnoldo98 commented on October 3rd 19 at 02:57
October 3rd 19 at 02:56
I think we need to look at the number of cores and bus width and caching. The logic of the 2 processors would be better.
October 3rd 19 at 02:58
Still, Yes, it was about a new slow cooker a workstation from Apple
www.apple.com/mac-pro/

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