Windows 10 "Affinity"

[wangyuji431]

I was wondering whether the settings to set programs to use only specific cores actually improved performance.

Like if I were to set photoshop to render using two cores in an eight-core processor, or having the windows system only use the last two cores for disk defrag, etc?

Thanks!

[runit3]

I was wondering whether the settings to set programs to use only specific cores actually improved performance.

Like if I were to set photoshop to render using two cores in an eight-core processor, or having the windows system only use the last two cores for disk defrag, etc?

Thanks!

Well there's a basic answer and a theoretical answer.

 

Basic: If you have overclocked your processor's cores to be synchronized, meaning each core is at the same mulitplier, there will be absolutely no difference.

 

Theoretical: If you have not overclocked your processor, and you are utilizing Intel Turbo Boost, yes, there actually will be a difference. Depending on the CPU not all of the cores turbo up to the rated specification. There is a core turboing scheme where only 1-2 cores turbo to rated, then the remaining cores decrease in multiplier. The difference will not be that large, however it may be noticeable for some tasks that are CPU dependent. 

 

Ideally, if you wanted the application to have the highest priority you would set it to cores 1 & 2, with your less important programs running on the remainder. The caveat to that is you will need to know how many cores your application can actually use, as setting a 4 core/thread application to only run on 2 cores will just decrease performance.

[wangyuji431]

-snip

Just for clarification, would that mean that a game only optimized for 2 cores can have the same performance should I limit it to CPU cores 0 and 1 while having another program using the other six cores?

[runit3]

Just for clarification, would that mean that a game only optimized for 2 cores can have the same performance should I limit it to CPU cores 0 and 1 while having another program using the other six cores?

Assuming you have a 5960X, yes, that would make sense. However, if you're referring to a 4 core 8 thread CPU, then only if assignment can be put on to the core and not a thread. Threads do not equal cores in terms of performance. If Windows is following a synchronous core assignment scheme like this:

 

Core 1 = CPU 0 ; Thread 1 = CPU 1 ; Core 2 = CPU 2 ; Thread 2 = CPU 3;

 

you would actually want the assignment on CPU 0 & 2 or CPU 0-3, for a total of 2 cores and 2 threads (4 "CPU's" as Windows labels them).

 

*edit* If you have an AMD system, like the FX-8xxx series, it won't matter in the slightest. AFAIK all AMD "cores" are synchronized relative to clock speed.

[incarnate]

With amd, the only way you'd see an increase is if the application required a lot of fpu calculations and was limited to four cores or less. Setting it to all even cores or all odd cores would put every thread on a separate module which would allow all for threads to use the fpu. However I don't think this would increase much in practice