Does Sim really only use 4-cores under load?

[TacomaSailor 187]

Techspot did an extensive set of benchmarks running on an ryzen 9 3950X with 16-cores and 32 threads.  They tested about 30 graphics cards ranging from a GTX 1650 to a 2080 Ti.  

What I find most interesting is this statement

So for now, DirectX 11-only means the game is not great at CPU scaling. As a result, Flight Simulator 2020 limits itself to using 4 CPU cores which is a waste, as we just saw in a lot of instances we were CPU limited with the 16-core 3950X, yet the game only uses 15 - 20% of the CPU. The same problem was seen with the Core i9-10900K, though the higher clock speeds do allow for a little more performance at lower resolutions. Still, the 10-core processor just saw 4-cores loaded to around 80-90%, with the rest doing very little.

Looking at the benchmark numbers - it appears the CPU(s) are the limiting factor.  At 1080p in Ultra mode there is no  practical difference in frame rate between the 2080 and 2080 Ti (45 and 47 average). And, in Medium mode there is no difference between a 1080 and a 2080 Ti (65 abd 66 average)

Can anyone verify that they never see more than 4-cores under heavy load while running FS 2020?

[EmaRacing 302]

No, I have all 12 cores doing things almost equally, these websites just look an easy comment to gain engagement or something.

[ChaoticBeauty 6,692]

It does use more than 4 cores, but supposedly it doesn't stress them as much. Quad-cores without simultaneous multithreading are choking a bit, which means that the extra headroom is needed in most cases. A 6-core CPU seems to be the sweet spot for now.

This probably applies to the higher settings though. I am running at the lowest settings and seeing very even usage across my 6 cores.

[Moria15 950]

Yeah some of these sites need to do a bit more investigation...

I have all my cores (8) running about even, but I have 4 cores running a little higher because yes, DX11 can only use 4 cores for graphics, but it doesn't mean the main program cannot use more doing other things.  Whilst the tech is complex, it is not unachievable as FS2020 shows when built to use the facilities available.

Multi-Core processing and Multi-Thread processing are 2 terms that a lot of people get very confused over, along with Hyperthreading and actually few people really understand overclocking and what it can and cannot achieve.

Graham

Edited August 24, 2020 by Moria15

[cwburnett 1,808]

I noticed yesterday that different conditions cause different cores to work. For example, I was parked at an airport and went from daytime to night time and watched CPU2 usage fall and CPU3 climb by material amounts.

Here's what 6 cores look like...clearly only half my cores doing a lot of work, except when the scenery loading stutter fest happens, then they all work at 100% and stutters abound...

[RichieFly 670]

I use a i7-8700K with hyper-threading enabled.

I see even utilization across all cores with the exception of 'CPU 11', which is sometimes maxed out. When maxed out, I'll see 'Main Thread Limited' message in the built-in FPS meter.

But, if I change settings to higher scaling and higher texture supersampling, I'm in the 'GPU Limited' range and the CPU is somewhat less loaded.

I've not spent much time tweaking (I hate tweaking) but it is reassuring to know the simulator is this dynamic, in terms of hardware utilization.

[cwburnett 1,808]

2 minutes ago, RichieFly said:

I use a i7-8700K with hyper-threading enabled.

I see even utilization across all cores with the exception of 'CPU 11', which is sometimes maxed out. When maxed out, I'll see 'Main Thread Limited' message in the built-in FPS meter.

But, if I change settings to higher scaling and higher texture supersampling, I'm in the 'GPU Limited' range and the CPU is somewhat less loaded.

I've not spent much time tweaking (I hate tweaking) but it is reassuring to know the simulator is this dynamic, in terms of hardware utilization.

Do you see the CPU spikes occasionally, like are seen in my screenshot?

Also it's odd that some people are reporting even distribution across many cores and others are seeing what I'm seeing, which is just a few cores working hard...not sure what to make of that...

[RichieFly 670]

cw,

The activity is very dynamic; I see big changes depending on the camera position/view and terrain. I see big spikes when (I assume) loading in new terrain. Also I noted, that the drone view is more taxing than the cockpit view. That seems counter-intuitive unless the drone view requires loading in more terrain. A lot going on there.

I hope they can fine tune the software to be equally 'good' with more hardware configurations. For me, it is a wonder just how smooth it all runs.

[cwburnett 1,808]

5 minutes ago, RichieFly said:

I see big spikes when (I assume) loading in new terrain

But these don't cause stutters for you?

When I tested on an i7 9700k instead of my i5 9600k, I noticed the spikes still, but the stutters were less pronounced. This anecdotal evidence, plus your input, suggests that more cores are more important that faster cores. My i5 cores are faster than my i7's (because of a better overclock), but that seems less important for this problem than simply having more cores to do whatever it is that's being done when CPU spikes.

[AbjectMaelstrom 7]

On on my 7700k with HT on I see utilization of all physical and virtual cores, averaging 50-60% load according to MSI afterburner. Zero stutter (minor stutters when new scenery loads, but it's barely noticeable it bounces back quick). 

Edited August 24, 2020 by AbjectMaelstrom

[RichieFly 670]

Yes CW,

I have pretty much no stuttering at all. Once or twice in the entire 10 hours I've been using it.

When first loading up a flight; during the cinematic portion I have jitters. But, once loaded and 'behind the wheel', no stuttering.