Whether HT is enabled or not - If the CPU is hotter it is doing more work. More work done = more heat.

@Cruachan, @kevinfirth and @Rob_Ainscough, thank you all for your views. All three know your onions as does @SteveW.

My CPU is a one-off. The i7-8086K has the first core designed to run at 5.0 but the remaining ones run at a slower speed. If any of you have info specific to that CPU it would be interesting to hear.

One thing that slightly confuses me. With HT enabled only half of the first core is being used. The second half barely registers as can be seen in Task Manager - Performance.

Now if I turned HT off all of that first core would be used wouldn’t it? That being the case wouldn’t that increase the amount of processing it could undertake?

Look at the diagram Chillblast provided below. My BIOS skills are minimal so I need to be careful.

https://www.avsim.com/forums/topic/603806-30fps-unobtainable-but-core-0-is-not-at-100/?do=findComment&comment=4577488

 

1 minute ago, Ray Proudfoot said:

One thing that slightly confuses me. With HT enabled only half of the first core is being used. The second half barely registers as can be seen in Task Manager - Performance.

Yes it is confusing but it is using the whole core even if only half looks used. If both halves are in use then the core is being shared to both logical processors (virtual cores). The main sim task on the used half is rendering the view so you need that to have maximum throughput of that core. If you have another task on that other half then the core is sharing throughput where you don't want it. It is easy to avoid that with HT disabled, with HT enabled you use the AM to stop P3D (or FSX) from using that second half with the binary '01' on the rightmost digits of the AM. That's why HT enabled and no AM reduces performance in the main task and HT disabled doesn't need the AM.

So here's the thing...with HT (or SMT) enabled means that each real core emulates two logical processors (LPs) they exist on the same real core and that core must do the work of two. No matter if you have HT enabled or not, the system of programs running on the CPU do exactly the same thing.

If the CPU is hotter with HT enabled it is because it does more work in the same time. The HT mode allows threads distributed across the LPs to complete faster and thus more heat is generated.

With HT disabled, less heat generated means you can increase the frequency a bit more which generates more heat.

The question remains, will increasing the frequency a little (clock rate) outweigh the HT mode? If the main task of P3D on LP0 is not at 100% then there's nothing to gain with a higher clock rate.

The HT mode can be used to improve the background tasks of P3D to improve the scenery loading and so on. This can be seen clearly by enabling more LPs the scenario loads more quickly because the scenery loads more quickly. That can be tested with a stopwatch, no special software is necessary and works on every system. Take an HT disabled PC and time the scenario load, switch HT on and see the scenario load more quickly.

When the simulator is running and the aircraft is moving into new scenery, that data is loaded faster and less stutters are evident. However the first core must be set up to only allow the one task on LP0 (Top left core). In the Task Manager graphs the second HT core LP1 (one in from the top left) should look dormant.

 

 

 

28 minutes ago, SteveW said:

Yes it is confusing but it is using the whole core even if only half looks used.

Thanks Steve. I trust what you’re telling me but it does seem odd that the whole core is being used when the graph suggests otherwise. Computers eh? 😁

Now to my CPU in particular. With HT enabled core 0 can run at 5.0. Am I correct in thinking that with HT disabled it would not run at 5.0 but at a lower frequency and if so, what?

Hi Ray, make sure that your power setting is set to High Performance and not Balanced.

Windows likes to change these settings without your knowledge and there have been several major updates recently (21H1).

If this is set to Balanced you may get stuttering and drops as the Core frequencies are decreased due to < 100% utilisation.

Edited July 27, 20214 yr by G MIDY

2 minutes ago, Ray Proudfoot said:

Thanks Steve. I trust what you’re telling me but it does seem odd that the whole core is being used when the graph suggests otherwise. Computers eh? 😁

Yes it is a complicated concept to grasp but the core is only emulating two cores. However the core is set up to do hyperthreading and that enables the threads that would be running on that one core to continue with less waiting by being distributed over the two LPs.

 

5 minutes ago, Ray Proudfoot said:

Now to my CPU in particular. With HT enabled core 0 can run at 5.0. Am I correct in thinking that with HT disabled it would not run at 5.0 but at a lower frequency and if so, what?

You would have to consult the documentation and experiment to see what can be done with that CPU in that system motherboard and memory. In your case, I imagine the PC comes set up reasonably well by the builder for best use and HT enabled as stock setting.

The only problem is that for P3D to benefit from the HT mode requires us to set the affinity mask adequately or the first core will be shared and that will reduce performance in the main task.

@G MIDY, where can I find that setting please? Bear in mind it’s a professionally built PC so all BIOS settings should be optimal already.

2 minutes ago, SteveW said:

Yes it is a complicated concept to grasp but the core is only emulating two cores. However the core is set up to do hyperthreading and that enables the threads that would be running on that one core to continue with less waiting by being distributed over the two LPs.

So even though only one of the two VPs on the first core is running at 100% in reality that’s the maximum that core can deliver. Got it. 👍

3 minutes ago, SteveW said:

You would have to consult the documentation and experiment to see what can be done with that CPU in that system motherboard and memory. In your case, I imagine the PC comes set up reasonably well by the builder for best use and HT enabled as stock setting.

Chillblast did recommend leaving HT enabled. They know more than me which is why I bought it from them rather than buy the bits and build it myself.

P3D v5 and all its revisions seems to have caused more issues than v4 ever did. DX12 I suppose.

Appreciate you guidance. 👍

8 minutes ago, Ray Proudfoot said:

@G MIDY, where can I find that setting please? Bear in mind it’s a professionally built PC so all BIOS settings should be optimal already.

On the Task Bar Start button, choose the cogwheel icon "Settings".

In "Settings" choose "Power and Sleep".

In "related settings" choose "Additional power settings"  (Control Panel\Hardware and Sound\Power Options).

Choose "Change plan settings" (Control Panel\Hardware and Sound\Power Options\Edit Plan Settings).

Choose "Change advanced power settings".

In that popup window you can choose settings for "Processor Power Management" and other items.

15 minutes ago, Ray Proudfoot said:

So even though only one of the two VPs on the first core is running at 100% in reality that’s the maximum that core can deliver. Got it. 👍

You got it Ray. 👍

 

15 minutes ago, Ray Proudfoot said:

Chillblast did recommend leaving HT enabled. They know more than me which is why I bought it from them rather than buy the bits and build it myself.

Good call.

 

15 minutes ago, Ray Proudfoot said:

P3D v5 and all its revisions seems to have caused more issues than v4 ever did. DX12 I suppose.

Maybe, but HT and Affinity Mask use as recalled by @Cruachan, @kevinfirth is still just as valid now.

 

15 minutes ago, Ray Proudfoot said:

Appreciate you guidance. 👍

The pleasure is mine.

Edited July 27, 20214 yr by SteveW

I've been experimenting a bit with HT on my overclocked 8700k. In theory it has single core boost capability of 4.7, but I have never seen that at stock settings. Stock it goes to 4.3, but I have it overclocked to stay at 4.5 when under load.

There is a thread here about the advertised maximum boost speed which shows that without a great deal of effort it is not realistic:
8700k doesn't seem to be boosting to 4.7ghz for single threaded applications : intel (reddit.com)

I definitely get more heat with HT enabled (maybe 3 to 4 degrees peak temperature). The only significant difference in the sim with HT enabled (even with an affinity mask to only use 1 LP per core) is that it does seem to load scenarios slightly quicker, but frames and stuttering are not materially better and the extra heat is not worth it IMO.
 

You can't increase frames per second unless the simulator draws less objects.

In general it is better to limit frames to that which can be maintained, and thus limiting heat. Either by using monitor refresh and VSYNC=ON or by externally limiting. With external limiting VSYNC=OFF is smoother but there will be frame splitting (tearing) when fast panning.

Loading the scenario faster equates to loading the scenery faster and is better when flying faster, or observing the scene to the horizon.

P3D settings determine the outcome of smoothness, HT enabled can only increase the total system throughput. If the heat is higher the total system throughput is higher.

Edited July 27, 20214 yr by SteveW

@SteveW, thanks for the guidance Steve. Chillblast have their own power management configuration and all seems well according to this screenshot.

3 minutes ago, SteveW said:

P3D settings determine the outcome of smoothness, HT enabled can only increase the total system throughput. If the heat is higher the total system throughput is higher.

I agree with this but for me the extra heat is not acceptable, especially when the room is warn and I get close to the thermal limits. The HT on sim is not noticeably smoother or more stable than HT off, given that I have my settings low enough that the sim is very smooth and stable in 4k with high resolution textures and no blurries / jaggies.