Increase in single core CPU usage after SU12

Just installed the SU12 and I’m noticing a significant increase in CPU usage. MSFS has always taxed one single core more than the others, but with SU12 this one core is seeing significantly more load.

There is a considerable drop in FPS, especially when taxiing and high air traffic areas. All the while the GPU is sitting pretty at less than half load.

I haven’t touched the setttings before/after SU12, I disabled the few mods I had too.

Has anyone experienced similar symptoms?

Core i9 9900KF with Radeon 6800XT in DX11 mode.

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Thanks. It’s been a while since I posted a new topic from scratch and the new forum categories are still a bit confusing.

Cheers!

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Do you see the same behavior with DX12?

I haven’t used DX12 in a while. Under pretty much all scenarios I see worse performance with DX12. I may have to give it a try again.

BTW, I am aware there have been improvements to live traffic density/accuracy in SU12, but turning off all air traffic in settings has no impact on CPU usage, nor does live weather.

Any chance you’re using FSUIPC for input management? There was a beta thread reporting slowdowns related to that (I didn’t follow the thread in detail; I use spad.next for input management and encountered no problems with it in beta).

Nope. Almost barebones MSFS install. The only mods are airport/scenery addons.

There was a SU release a long long time ago that had this same effect on my system, although at the time I had a different GPU. It got fixed in later SUs. I’ll do some testing and change/lower some settings but I suppose I’ll have to wait for further performance improvements.

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Well, going from DX11 to DX12 had absolutely no effect (perhaps a slight performance hit with DX12) but I found a thread about CPU usage and disabling virtualization in BIOS. I did that and went from 30 to 50fps sitting at the gate in high-traffic airports. No sim settings touched.

Maybe SU12 is even more sensitive to virtualization being enabled system-wide? I’m amazed at the improvement and also confused, but for now I’ll just take the gains.

I do notice that with virtualization enabled, the highest loaded cores rarely went past 70-80% and now they are hitting peaks of almost 100%, so that’s good.

Wow, that is a huge gain. I suspect you need to update your bios as there was a fix by AMD that came out with around spring 2022. The varios vendors worked it into their bios by around May 2022. You will then be able to re-enable virtualization

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Yeah, I was very surprised too. I don’t use virtualization too often and when I do I can simply jump back to the BIOS and flip the switch. I had virtualization ON and VT-d (or -x?) OFF. Turned everything OFF and I got 15+ fps in CPU bottleneck situations. I have no idea what that change frees up, but I do see the most loaded CPU core going higher than ~80% utilization now (whereas that didn’t happen before).

MSFS multi-core implementation is weird. Considering there is still one core that gets overloaded and bottlenecks, I would actually like for MSFS to let other cores idle more since I could push 1 or 2 cores to a higher overclock, but since basically all cores have at least some marginal load, I can’t.

I assume that BIOS fix is for AMD processors? Mine is an Intel so I guess it doesn’t apply. In any case, I’m on the latest BIOS for my motherboard.

Have not noticed this…core/FPS performance has been pretty consistent for me from SU11>SU12 Beta>SU12. By any chance did you clear your rolling cache? Doing so can really mess up performance. Especially since the FS servers are so busy right after an update. Also, did you check your graphics settings? For odd reasons, settings can get changed during these updates.

I’ve never seen any of my cores pegged at 100% since MSFS was released. Something in the 80’s % was the most I could always see:

image

Disabling virtualization made that last core go a bit higher, to the low 90’s %. Here is the stock A320 sitting at Houston at an extremely busy time and FPS in the high-40 low-50 range (I changed Afterburner’s core monitoring to just an average, sorry. I can’t stand the whole list blocking my view for too long):

A bit lower in the air close to the airport with so much traffic around, but still smooth:

So overall I’m happy now but I did see a definitive increase in CPU bottlenecks after SU12 for some reason. I also pushed the CPU a bit more to 5Ghz at the expense of some heat but it’s been stable.

Yes I can’t say for sure it’s SU12 because there have been a few Win11 and NVidia driver updates recently but my system is struggling where it didn’t before. I’ve got a pretty high end machine tuned up well for MSFS and with DX12+Frame Gen on I’m back to slide shows in high traffic scenarios (VATSIM) which I’ve not had since before the 4090. It’s the CPU working hard not the GPU. 5800X3D 4090.

It heavily leans on the mainthread, but there’s still a significant amount of other cores handling other loads.

Because you’re seeing the usage by thread, not by core. There are two threads to one core due to hyperthreading. One of your cores will be near 100% on the mainthread - check out your #16 thread at 83%.

Just want to confirm I experienced almost the same issue - i am running a ryzen9 5900x with a 6800xt card. I noticed immediately after the latest update there was about a 15-20c increase in cpu temp and useage was way up. I tried adjusting/decreasing the power option in windows which lowered the temp but then my GPU started running hotter. I then tried undervolting the GPU but that didn’t stick. So my choice now is do I want to put more stress on my CPU or GPU. I had such a smooth running game with a nice balanced workload on the CPU/GPU - temps on both in the 55-65c range when running the game. It seems like with every update comes a new set of issues. I know I’ll work it out eventually but man how I wish there was a way to opt out of future updates.

I’m also running a Ryzen 5900x with a RX 6800 and I did not notice any differences with my CPU or GPU after the last update (SU12). Perhaps a review of your sim settings would be a good idea - especially ensure in the graphics settings its set to FSR2 and balanced mode. I have found that setting along with T-LOD impacts my CPU/GPU the most.

Edit: I use the AMD Ryzen high performance power plan with my CPU OC’d and undervolted.

Good luck!

I also notice worse CPU-performance and higher temp-spikes compared to SU11. Very annoying because I don’t have much margin between stuttery and smooth flying locking my fps to 30 with an older i5-9600kf.

I already deleted rolling cache and nvidia shader cache. I also checked my settings which are still the same.

I’ve had similar - I tried runway 08R at Gatwick yesterday. All good until lining up on the runway where then the main thread decides to go a little wild and fps drops. Happens when lining up or coming into land.

I can’t recall it happening during the Beta - even dialling down settings doesn’t seem to improve things.

Let’s hope it sorts out - if a video would be useful I can do one to demonstrate.

After the sim update 12 I have a similar situation where cpu utilisation becomes erratic when I go above FL200 and frame rates jumps all over the place. Strangely, cpu utilisation and framerates goes back to normal below this altitude and on the ground. Setting graphic pre-set to High (usually Ultra) also had no impact on this issue. RTX3080, 5800x3d, 32gb ram

Oh, of course! I always forget that what afterburner shows as “CPUs” are actually threads. So in that screenshot CPU15 and CPU16 are the same core and it’s actually reading a bit over 100%. Thanks for the refresher man, I went down the rabbit hole trying tweak settings to hit as close to 100% in a thread as I could.

I’ve read that for some folks completely disabling hyperthreading reduces CPU bottlenecks. I haven’t tried that.