15 minutes ago, Bert Pieke said:

Render scaling of 120 on the 1080 monitor should be roughly equivalent to 100 on the 1440 monitor.

So dialing that back makes sense.

Yep, that was my thinking Bert, but see my post above saying that unbelievably, switching to DX12 completely fixed it.  I can offer no explanation of how or why though. That remains a complete mystery to me, since when I tried it a while back, I saw no advantages to compensate for the loss of 4 or 5 fps.

Hi Cianpars, I started a thread yesterday which could be related to your issue. Basically, all of a sudden I started experiencing some weird FPS drops, from stable 30-40 to unplayable 10-12. Sometimes these drops go away, but in most cases they stay for good and the only way to come back to normal performance is to cancel the flight of course and go back to main menu. It can’t be anything hardware related as the sim had been running smoothly before. This issue occurred unexpectedly yesterday without ANY change in my hardware nor in community folder. 
 

What’s more, some other guys confirmed in the thread they too had experienced such a problem which leaves me thinking it must be something related to MSFS itself and its servers. Maybe you are dealing with the same thing?

 

edit: a lot of reports on MSForums from people having a quite similar problem in this thread: https://forums.flightsimulator.com/t/after-playing-a-few-hours-fps-drops-from-40-to-5fps/389603?u=tyrannicsiren6

 

Edited January 2, 20224 yr by lemonid

Thanks Lemonid.  I don't think so as it became an issue as soon as I connected my new monitor.  In a bid to resolve, I resorted to moving to W11 (which handles HDR better than W10) then updated Nvidia, chipset and mobo drivers.  Played around with settings for a couple of days and nothing really helped much.  Finally, thinking it could do no harm, I switched to DX12 mode and wow, everything was back as good as before.

It is possible that moving to DX12 may have reset something somewhere, I suppose.  I may try going back to DX11 later and see what happens to confirm, though part of me has had enough of tinkering for a bit.

Well, I’m no expert but it seems rather odd to have a software issue just because you connected a new screen. Have you tried checking what happens if you plug the old one back in? Also, I think I saw someone in another thread state they were able to regain normal functioning with DX12 on, oddly enough. So maybe it’s not hardware related after all in your case, since a lot of people are experiencing these weird FPS drops now. Just a thought. 

On the runway at my local airport  this morning at 45 fps in dx12 mode.  Went back to the same scenario in dx11 mode this morning and back to 26 fps. Straight back to dx12 mode for me and back up to 45 fps.  I'm getting 70 fps cruising over SW England at 2,500 feet too.

I really don't know why dx12 is making such a difference, but I'm not complaining.