How to Set CPU AFFINITY without using FSX.CFG

[DavidCG 0]

I have found that using[JOBSCHEDULER]Affinitymask =14or any value in the FSX.CFG file does not work. Running FSX and looking in Task Manager, the CPU Affinity is always set to all cores.However, if you create a shortcut with the target at followsC:\Windows\System32\cmd.exe /C START "" /AFFINITY E "D:\Program Files (x86)\Microsoft Games\Microsoft Flight Simulator X\fsx.exeThis will correctly set the affinity to cores 1,2 & 3 leaving core 0 free for the system.This will also work for any program, just change the relevant path.Just thought that you would find this interesting!David Gunton

[JSkorna 137]

I know my affinity mask works looking at the Task Manager graphs.

[tipitout 5]

So does mine. If I delete the affinity mask entry, the difference both in FPS and in the graphs is dramatic.

[JSkorna 137]

Exactly why MS put it in!

[wanabflyer 53]

A little bit lost in translation here. Are you saying the Affinity mask entry should be included in the FSX config or not? Just curious.

[JSkorna 137]

Yes and set to 14 with a quad core system.

[wanabflyer 53]

A little bit lost in translation here. Are you saying the Affinity mask entry should be included in the FSX config or not? Just curious.

Then i'm all set. Thanks.

[Pete_Smith 1]

With affinitymask=14 in my fsx.cfg file, while at dense airports, my core0 runs at around the 20% processor usage mark, while core1, 2 and 3 run at around max.Using the cmd line shortcut above, my core0 runs at 2 to 3 % max and core1, 2 and 3 run, again, at around 100% at dense airports.Interestingly, after much experimenting this evening, using affinitymask=12 (i.e only using core2 and core3), my fps increases about 2 or 3 fps at dense airports compared to affinitymask=14. Strange but seems so with my pc. These results were found after alot of experimenting and comparing. Flying was smooth. I'm using a 4 core i5-760 running at 3.8ghzIn order of fastest fps to lowest:1. Affinitymask=122. Affinitymask=143. No affinitymask4. the above cmd line shortcut.I will use Affinitymask=12 for now and see how it goes.Regards,Pete Smith

Edited February 27, 2012 by Pete_Smith

[JSkorna 137]

14 means that core zero is not used with core 1, 2, and 3 being used. The idea is that OS and other software runs on core zero.Really not sure of the syntax for the command line, but it is sure not good for you.I have never tried 12.

[XCLTM3 112]

With affinitymask=14 in my fsx.cfg file, while at dense airports, my core0 runs at around the 20% processor usage mark, while core1, 2 and 3 run at around max.Using the cmd line shortcut above, my core0 runs at 2 to 3 % max and core1, 2 and 3 run, again, at around 100% at dense airports.Interestingly, after much experimenting this evening, using affinitymask=12 (i.e only using core2 and core3), my fps increases about 2 or 3 fps at dense airports compared to affinitymask=14. Strange but seems so with my pc. These results were found after alot of experimenting and comparing. Flying was smooth. I'm using a 4 core i5-760 running at 3.8ghzIn order of fastest fps to lowest:1. Affinitymask=122. Affinitymask=143. No affinitymask4. the above cmd line shortcut.I will use Affinitymask=12 for now and see how it goes.Regards,Pete Smith

Hi Pete,I understand what you're getting at. I've seen this mentioned at Tom Tsui's website "FSX Times" where he toyed around with the affinity mask at several different settings and the results he obtained with them. Very interesting indeed.I've decided to tinker with mine a little to see the effect.Rgds,

[VOR_Active 4]

Excuse my ignorance but what exactly is Affinitymask?

[JSkorna 137]

Hi,It's a setting in your FSX.cfg file that instructs FSX as to what CPU cores to run on.

[VOR_Active 4]

Thank you Jim. Allow me one more question. The numbers Affinitymask=12 or 14 what are their logic? The highest the value the better performance?

[Jet_Airliner 0]

What affinity we need to use 4 cores? I don't want 3 cores

[JSkorna 137]

Four cores = 15It's using binary code ( zeros and ones) then adding the position values from right to left.Like the affinity mask of 12 is using core 3 and 4.An affinity mask of 8 is core 4 only.