It also depends on your use case.
If you’re GA flying with a cessna, etc., from smaller airports, you can absolutely push the LODs. And the GPU can take on the rest of the settings as well without issue.
But if you’re doing airliner flights, with 3rd party aircraft, 3rd party airports (or default handcrafted) then you can’t really push the LODs. I’ve been trying out Dallas default handcrafted with the Fenix A320 (Which is not the worst 3rd party for vram) and with Rebar ON, it’s just a stutter-fest on high-end preset.
Then, turning Rebar OFF makes the CPU work a lot more as it’s pushing all the little chunks to the VRAM, so even if you stay on the limit of available vram, you have a lot more stutters. That’s what rebar is meant to fix but it doesn’t matter, because with Rebar ON, you only have 12.2GB usable VRAM and you’re hitting that limit a lot sooner.
And it doesn’t matter what AMD and Nvidia were thinking about. The sim needs to cater to the addressable market, not the other way around. Ideal specs are listed as 12GB VRAM. That should handle anything default thrown at the sim, at least on High-end preset if not more. We can’t keep blaming user PCs when with 16GB Vram on HIgh-end preset (not ultra) at Dallas default handcrafted airport I punch through the vram limit. And it’s a terrible user experience when you have to fiddle so much with bios settings, sim settings and whatnot, when running an above-ideal-spec PC.
I just bought a 9070 XT to upgrade my sim experience and I got 2 days of changing bios and sim settings to get it to run without stutters (even then, not always without). For my use case at least. But what should I do ? Return the 9070XT and get a 5090 ? Or an older-gen 7900XTX without new tech just for the VRAM ? not much to choose from and I’m seeing even those people complaining about not having a smooth experience.
In reading through all the threads it looks like disabling ReBar via NVPI vs at the BIOS level will do the job. I’d prefer that method that way I can have separate profiles for 2020 and 2024.
Question: Does enabling/disabling via NVPI require a reboot?
I’m trying to set again the ReBar on… as I would like not to tweak so much my PC before playing a game… So far my statement is :
_ VRAM usage in the MSFS FPS display is increased by more or less 1GO (on a 3070 ti last drivers 8GO)
_ VRAM is going above the maximum figure shown in the FPS display (it is like : 7,2 GO/6,98GO)
But…
It seems, that I’m less suffering of the stutters after 1 hour of flight with the fenix, or yhe CRJ. It seems that frame rate is more consistent (even if it is lower)
With RE BAR off, i set 60 FPS max, and can reach 120 once FSR3 FG is activated.
With RE BAR on, with same config, I can achive 80 to 90 FPS (never the 120) but… it seems to be a little bit smoother…
So I will to set 30 FPS max on cfg file, to have consistant 60 FPS… It could work. I will also limit the frame rate of my monitor to 60 so everything is aligned…
If I can get rid of the landing/takeoff/after 1 hour stutters i had… well I will tell you !
I sold my 4070 since I play on 4K and it’s started to be insufficient in some scenarios, msfs24 included.
So i bought a 7900XT. Fired up the sim, 4K downscaled to 90%. Everything ultra, except texture res which was on High. Rt shadows off. No AI. INI A350, 3rd party airport.
The sim stutters like hell, fps drops to the “negative”. So I had the exact same issue just like with my 4070. Lol. It’s just eated up all my available vram which is 20GB in 7900XT. “Peaked over retail budget” etc.
I tried a lot of option to “fix” this issue but nothing helped. FSR upscaling ghosting is horrible in glass cockpits speed and altitude tape, and on the screens in general so it was not an option for me.
I rage uninstalled the sim a couple of times, lol. Even I nearly started to sell my every flightsim hardware and go back to simracing.
But I saw this topic, first time I hesitated to turn off rebar or even try this solution as a last resort. But holymoly… This only one thing solved all my issues with the sim. I could run everything on ultra with the same scenario which eated up all my vram before. Now with high texture res, 90% res scale, A350, JustSim LFMN my vram is 13-14 max. Before it was 17-18. My total available vram went back to ~20GB without rebar from 16 with rebar on.
So regarding the memory management something isn’t right with this sim… 20GB for 4K even with addons should be more than enough imo even nowadays.
Thank you for this tip, it’s saved my hobby and my mental health…
Everybody who have vram overusage ou stutters should test ReBar OFF
It’s not difficult to implement and you can go back if it doesn’t have a positive effect on your setup.
For me, it made MSFS 2024 smoother, much more smoother.
Now, with last version su2 1.4.18, fluidity is at is best level, almost perfect with ultra quality, TLOD 400. Most of the time msfs 2024 uses 8G out of the 16G of vram in 1440p.
That said, i don’t use those airliners that kill vram… It’s clear that something is wrong with these airliners. Poorly optimized ? Textures too heavy ?
Mate, thanks for posting this. I just wrapped up evening 3 of BIOS tweaks, playing with sim settings etc and feel like I have achieved very little.
My system is 9080XT, 7800X3D, 32Gb - so a little weaker than yours but still very capable.
My issue is that I get good frames but stutters as I turn the aircraft towards terminals, areas with lots of airport LOD.
My test is to fly a short final, land, taxi in with overcast clouds on Fenix A320.
RBAR off definitely improves camera panning stutters and FPS but I get horrible stutters on landing (like the aircraft jumps down the runway) at Asobo EGLL with Fenix A320 (RBar on reduces these stutters)
My other test airport is ORBX YMML where I get far better frames and less stutter.
My main conclusion is RBAR is no magic bullet and EGLL handcrafted is a horribly optimized airport.
So my very limited technical understanding of ReBAR seems to point towards this issue being a result of Asobo potentially optimizing multithreading too well for 2024.
As I understand it, the purpose of resizable BAR is to allow for a much higher number of transfers of data/amount of data in each transaction from the CPU to the GPU. Users have reported little to no impact when disabling ReBAR in 2020 and my theory is that this is because 2020 already has a bottleneck slowing transfer from CPU to GPU.
But now with that core sim bottleneck removed, the CPU is now overloading the GPU causing the VRAM overages we all know and love. Disabling ReBAR effectively turns on a small bottleneck, preventing the CPU from overloading the GPU as easily. This explanation also helps understand why it doesn’t affect everyone equally, depending on where your natural bottleneck already exists.
Erm, also try wiping the rolling cache (and don’t forget to put it back up to like 32GB in the settings menu). There’s a bug there as well where it fills up and then you just get stutters everywhere.
@Zadma i don’t know man, it’s not overly stressing my CPU. The only stutters that appear are when it reaches and goes over-limit. The limit being lower than what I actually have in my system. Windows shows only 13/15.5 used, and in-sim I only have 13.something available. You’d think it reserves some buffer so it can be smoother, but as soon as it hits that in-sim limit, it pops the message and starts stuttering. And the problem was the same in MSFS2020, it was just obscured by the absurd mainthread limitation (which caused more stutters), but that sim can also easily gobble up 16-17GB of VRAM out of not enough available. 17GB of VRAM didn’t even exist on video cards at that time when it was released (joking, I don’t know, i don’t care either ).
I think you are right, as I observed, if I turn on ReBar, both of my CPU and GPU lag are high on high demanding airports with complex airplane like A350.
When turn off, only CPU lag is high, and also the VRAM usage is bit higher when turning on
(joking, I don’t know, i don’t care either