CPU affinity setting

[PaulGR 168]

This is something I am not sure about...
I will be overclocking my 8700K to same clock on all 6 cores but want FSX to operate on last three (HT off for FSX and on when I'm working) leaving the other 3 for everything else.
I will set FSX default affinity for specific cores so I don't have to do it manually each time when I run it.

Now, my question is regarding the affinity setting in CFG.
Do I leave it stock (created by default) or should I tweak that number only for the 3 that FSX will be using?

Also will FSX take into account when creating CFG values when HT is set to off or do I have to take this into account and set it manually as well? I never ran it with HT off so not sure how this works but figured since I'm going after (hopefully) 5.2GHz I'm just going to try and maximize performance on all counts.

This whole thing still confuses the hell out of me.

Cheers.

[Bert Pieke 7,585]

You cannot easily turn HT on and off other than changing it in the BIOS.

Since you are confused about the matter, I would suggest leaving it all on default. 

You are unlikely to make FSX performance better, and likely to make it worse. 

[PaulGR 168]

16 minutes ago, Bert Pieke said:

You cannot easily turn HT on and off other than changing it in the BIOS.

Since you are confused about the matter, I would suggest leaving it all on default. 

You are unlikely to make FSX performance better, and likely to make it worse. 

I know this is a BIOS setting and I know how HT works. Been running networked render farms for a while now :)
What I am trying to understand is if FSX calculates that value by itself having in mind my specified cores designation or I have to do it manually for this whole thing to work as intended.

Truth to be told I had everything working fine with HT on on my old system but if turning it off will give me some sort of performance upgrade then I want to give it a try.
 

[lownslo 592]

1 hour ago, PaulGR said:

Now, my question is regarding the affinity setting in CFG.
Do I leave it stock (created by default) or should I tweak that number only for the 3 that FSX will be using?

Also will FSX take into account when creating CFG values when HT is set to off or do I have to take this into account and set it manually as well?

FSX knows nothing about CPU affinity.  There is no “stock” setting in the CFG... the user must add their desired affinity setting to the CFG.  As well, FSX knows nothing about HyperThreading... it only sees Logical Processors (cores).  For your 8700K, 6 w/HT off or 12 w/HT on.

HTH,

Greg

[MDFlier 2,031]

Here's a simple way to determine Affinitymask. If you have more than 6 cores, simply keep doubling the "value". Add in only the values for cores you want turned on. 

HT disabled - Last 3 physical cores only

Core #   State  Value

Core 0   Off     1

Core 1   Off     2

Core 2   Off      4

Core 3   On      8

Core 4    On     16

Core 5   On       32

Affinity mask = 8+16+32 => 56

With HT enabled - Last 3 cores + HT used

Core #   State  Value

Core 0   Off     1

Thread 0 Off    2

Core 1   Off     4

Thread 0 Off    8

Core 2   Off      16

Thread 0 Off    32

Core 3   On      64

Thread 0 On    128

Core 4    On     256

Thread 0 On    512

Core 5   On     1024

Thread 0 On    2048

Affinity mask = 64+128+256+512+1024+2048 => 4032

[Bert Pieke 7,585]

https://www.binaryhexconverter.com/decimal-to-binary-converter

[MDFlier 2,031]

4 hours ago, MDFlier said:

Oops. I forgot to change the thread numbers... Corrections underlined. 

With HT enabled - Last 3 cores + HT used

Core #   State  Value

Core 0   Off     1

Thread 0 Off    2

Core 1   Off     4

Thread 1 Off    8

Core 2   Off      16

Thread 2 Off    32

Core 3   On      64

Thread 3 On    128

Core 4    On     256

Thread 4 On    512

Core 5   On     1024

Thread 5 On    2048

Affinity mask = 64+128+256+512+1024+2048 => 4032

 

[PaulGR 168]

Thx very much for this!

[PaulGR 168]

I got it set up and FSX is literally on fire.
I get stable 40FPS+ (airport area) and up to 70+ in the air in VC using NGX with traffic at 70, clouds in AS16 set at 140, LOD Radius 5.5 and generally everything max apart from autogen which is on normal.

I disabled HT on my new 8700K (dunno why I bought i7 now that I am thinking) so I can push it harder. Works stable like a dream at 5.1Ghz with temps under 80. I'm ok with that, purchased intel OC warranty so if it degrades I'll send this one for a swap.

The only issue I have now that FSX is using all those 3 cores at 100%. I'm pretty sure that on my previous build only one core was always at 100%. Any ideas? 3 cores left for other apps running is not that much. Some actually lag.
I have set up affinity using Steve's DX10 fixer and works great but why 3 at 100% in VC and 2 in outside view?

Any ideas?