ReBar causing VRAM overusage and decreases available VRAM amount in MSFS 2024

User Support Hub Install, Performance & Graphics
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TLDR: Game hates ReBar, game is still broken. If you’re maxing out on VRAM, experience stutters, fps dips and have ReBar on, DISABLE IT in your BIOS.

I used the same starting point of a career mission as a testing spot (urban - LIPU airport).

9070 XT
ReBar On - High textures/100 terrain quality (both settings really heavy on VRAM)/1440p TAA - available VRAM is decreasing during gameplay to around 13,2 GB’s. VRAM usage maxing out. Terrible stutter and FPS freezes when moving the camera around.

ReBar Off - Same settings, available VRAM is 13,7-14,63. VRAM usage not going over 12 GB’s, mostly around 11. Freezes and stutter gone.

Longer story:
I upgraded to 9070 XT from 7900 XT, its a 20 GB card, i also had some really bad drops/freezes when moving the camera when i was using it, but benchmarks were showing some decent FPS improvements compared to the XT so i hoped for a better experience.

But it was horrible, really bad FPS drops when looking around, way worse than on the XT, dev mode graph revealed that my VRAM was getting hammered. I really began thinking the extra 4GB’s on the XT are what made it a smoother experience.

But there was one change that i’ve made after upgrading. I enabled ReBar in the BIOS. Out of despair i Googled whenever rebar can have any noticeable effect on the VRAM. Some posts claimed increased VRAM usage with it on so i gave it a shot.

And boom, just like that, the VRAM usage went down, and the amount of total VRAM has increased, freezes are gone. Now i can even run Ultra texture settings with very few dips here and there.

This game is still a mess though, just messing with the settings, no matter if you increase them or bring them down makes it act up and introduce many performance issues, bugs. leaks, whatever you call it. It’s really hard if you’re trying to figure things out.

I will test some more when i get to it, still don’t know if this fixes the Fauna/Marine traffic lag and such.

Hope it helps someone, cheers.

------- EDIT ---------

If you’re not sure if you have ReBar on you can download GPU-Z to confirm, works for both Nvidia and AMD cards. (not my screenshot)

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Disregard, I saw that you have an AMD card.

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Same experience here as the thread opener regarding rBAR (RX9070 here with 16GB VRAM), thus not using it. Haven’t tried with latest SU2 yet but exactly same experience with current Syu1

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SU2 is the same. I actually opted out of it and completely reinstalled the game yesterday, when that didn’t help, turning off ReBar was the last thing to try on my list before uninstalling, glad it worked.

I won’t reinstall SU2 though, some people claim it carries some VRAM fixes but right now im just happy i can finally play again and want to progress my career mode.

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Hey man, I got the 9070XT on release day and was pulling my hair out until I saw your post… I was having a lot of stutters on the ground, sometimes in flight, with massive FPS drops—it was almost unplayable (even on SU2 beta)… I had resigned myself to going back to the 2020 version until I tried disabling ReBAR as you suggested, and the game is now smoother than ever… Thanks a lot for your post, I hope others in the same situation will see it and manage to fix the issue. Please, Asobo, fix this!

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Question: do factors such as motherboard manufacturer, BIOS and potentially BIOS revision, as well as GPU driver support, make a difference here?

This is academic for me as an Nvidia owner, but knowing these details might help make a difference in figuring out if disabling ReBAR helps or hinders in any person’s particular case.

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Not sure, I know that AMD called the option ‚SAM‘ but it now in the driver software shows up as rBAR.

I can confidently say my drivers and BIOS are the latest versions. Maybe it’s working with different games (not tried) or MSFS especially suffers from high VRAM usage and other games don’t bother.

A fact is that the utilisation is beyond the amount of VRAM being used without rBAR. But that should not be how it works? Doesn’t it just allow a more efficient data access to the VRAM?

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It is not necessary to disable RBar from BIOS. You can do it from the NVIDIA Profile Inspector directly.

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But the problem seems to concern only AMD cards :sweat_smile:

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Not necessary; I have an RTX 4090 and also see the overusage with ReBar enabled, especially in VR and panning the view to any side.

My rig is:

Ryzen 9 7950X3D
RTX 4090
64 GB RAM DDR5 6000 Mhz
4 SSD of 2 TB each

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Topic moved from Bug Reports to a more appropriate category.

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I’m assuming you disabled REBAR from your comment above. REBAR is supposed to optimize data transfers between your cpu and gpu and it is recommended to turn it on. If the sim is using more vram than what is physically present on your gpu I recommend that you turn on FSR3 and start with quality mode and step down from there until you safely keep under your vram limit.

MS/Asobo are saying the vram oveflow issue will be fixed in SU2 so we’ll see soon.

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I had issues with my VRAM filling up when flying over NYC with New York City Times V2 installed. I have a RTX 4060ti 16GB and AMD Ryzen 9 7900X and I’m in the BETA 2 and my Texture Res is on Ultra, as anything below, I notice the drop in quality especially in VR. I had ReBAR enabled so I disabled it and like magic no more VRAM over usage and overall smoother performance in VR.

So for now I’ll leave it off till the next SU.

Edit: I haven’t yet tested the differences with ReBAR off in MSFS2020

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If you have an AMD GPU instead of Resizable BAR, which is a universal standard, AMD uses its own technology called Smart Access Memory.
It works similarly but is optimized for Radeon GPUs.

For Nvidia GPUs Resizable BAR works differently and depends on optimizations for specific games.

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I think the CUDA-System Memory Fallback policy in NV control panel is more related to the VRAM issue

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on which level are the settings set…?
Under “MS Microsoft Flight Simulator 2024” or under “_GLOBAL_DRIVER_PROFILE (Base Profile)”

Could you send me a screen where I can see this in more detail…

I don’t understand where you have to set this…

Many thanks for your help…

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I use the 7900X3D and also have a 4090, where do I have to set what exactly in order to use the frame rate mode optimally…

I use the latest files via the DSSL Swapper in conjunction with the Nvidia app.

Many thanks

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Thanks for your suggestion!
Turning off Rebar in my BIOS has really improved performance on my setup

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Can we change something on this, have you got a recommandation ?

I turned of today the resizable bar, and the hardware scheduling… and it has improved performances. But it still terrible on take off and landings…

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an interesting aspect, there is a setting for ResizableBAR in my Asus bios that is set to “on”, but in the Nvidia Profile-Inspector it was previously set to “off”…what is the significance of this?

In GPU-Z resizableBAR is also shown as “active”…

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