News Nvidia GPU owners may be losing performance because of a simple setting that's disabled by default — enabling Resizable Bar with Profile Inspector...

[mitch074]

ReBAR on fully AMD system running Linux here. No problem whatsoever. Nvidia's drivers : the more intricate the plumbing, the easier it is to clog up the drain.

 

[pf100]

Resizable bar is a shitshow when it comes to nvidia because they don't care about it. They made a bad whitelist and have made no effort to update it. You're on your own.

 

[Assmar]

I went from 18767 to 19093
AMD Ryzen 7 5800X3D
NVIDIA GeForce RTX 4080 SUPER

 

[_D_D]

I just tried on my 3070 and Port Royal, no improvement so far...

Maybe try free GravityMark bench under Windows with d12, you'll need to add the nvidia profile yourself.

I haven't seen a profile setting for Linux, just fixed maximum aperture size but at least nvidia-smi shows BAR1 usage unlike Microsoft.

 

[SayAgain]

Seems like an interesting PCI express interface technology ... from what I've read resizable BAR needs to be enabled in EFI/BIOS in addition to GPU profile?

Does anyone else have some metrics using ReBAR with nVidia 5090 in MSFS 2024?

Rob.

 

[_D_D]

from what I've read resizable BAR needs to be enabled in EFI/BIOS

Not really but perhaps it's convenient to do it that way rather than POST BIOS. Some years ago Microsoft stated their driver would do the necessary resize but AFAIK that didn't happen.

https://learn.microsoft.com/en-us/windows-hardware/drivers/display/resizable-bar-support

On GPUs that support a resizable base address register (BAR), Windows will renegotiate the size of a GPU's BAR after firmware initialization in Windows Display Driver Model (WDDM) v2 and later.

 

[SayAgain]

I’ll have to do some testing on my PCs.

Unfortunately the drivers for my nVidia 5090 are problematic and cause texture corruption in certain areas within MSFS 2024 at higher LOD settings. The same settings and locations in MSFS 2024 on my other PCs using AMD 9070XT and another using AMD 7900XTX don’t exhibit any texture corruption (all with ReBAR disabled).

With that said, I do want to test ReBAR setting to see if it generates any additional issues (using both GPUs to compare) and relative differences in performance if any.

 

[HardwiredWireless]

That's not what jaytwocents said. He literally said it was a bug in Nvidia driver that disables rebar although it's enabled in the BIOS. He was mocking Nvidia like they were so dumb for doing that. Another youtube video filled with ignorance and misinformation.

Rebar is disabled globally by default and enabled only when the game benefits from it since plenty of games don't work well at all with it. This is a well known feature that anyone who messed up with rebar in the last couple of years is aware of. The problem with jaytwocents is that he is not a gamer (he pretends to be one for his ads but he doesn't game), so he doesn't know those things.

Now plenty of people who watch this video will enable rebar globally and then come on forums like this one to seek help because their games keep stuttering and crashing. And Tom's Hardware is spreading it.

World of Warships is actually a real game.

 

[snemarch]

Not really but perhaps it's convenient to do it that way rather than POST BIOS. Some years ago Microsoft stated their driver would do the necessary resize but AFAIK that didn't happen.

https://learn.microsoft.com/en-us/windows-hardware/drivers/display/resizable-bar-support

You do need BIOS/UEFI support to be enabled – Windows won't renegotiate the BAR size if it's not enabled.

I manually patched in BAR support (look for e.g. ReBarUEFI if interested) for an X99 board firmware that didn't have official support, in order to use an Intel ARC card. Made quite a big performance difference.

 

[SayAgain]

I ran some ReBAR On/Off tests last night with MSFS 2024 and for all intense and purpose my FPS was the same (within 1 FPS margin of error). I performed the same flight and same location(LEIB) /aircraft/weather/etc. and graphics settings and recorded both with RTSS overlay.

Test Hardware:
MSI X870E Godlike (rev. 7E48v1A34 … not latest UEFI but close) ReBAR enabled by default
AMD 9950X3D CPU
nVidia 5090 OC Trio (PNY) (driver version 576.80)
2X48GB 6400Mts RAM
Samsung 9100 M.2 2TB

Test Software:
MSFS 2024 SU2 all graphics settings maxed out using SSAA (aka TAA=200), DLSS not enabled (no frame gen)

Confirmed ReBAR:
UEFI - Advanced - PCIe SubSystems - ReBAR enabled
GPU supported and enabled (HWINFO)
nVidia Inspector to set the 3 ReBAR values (both Global and specific to MSFS 2024)

I’ll post side-by-side video later (if we’re allowed to link videos not monetized?).

In my case/settings ReBAR made no difference.

Rob.

 

[_D_D]

You do need BIOS/UEFI support to be enabled – Windows won't renegotiate the BAR size if it's not enabled.

I manually patched in BAR support (look for e.g. ReBarUEFI if interested) for an X99 board firmware that didn't have official support, in order to use an Intel ARC card. Made quite a big performance difference.

I also have an X99 (Taichi) and didn't have to modify firmware to set Resizable BAR. Above 4G can be left disabled in BIOS as it's just a hint. CSM can be enabled too while GOP UEFI driver is also enabled.

I've never seen Windows 10 "renegotiate the BAR size" so if you can show this actually happens that would be great.

@SayAgain welcome to Resizable BAR for nvidia

 

[snemarch]

I also have an X99 (Taichi) and didn't have to modify firmware to set Resizable BAR. Above 4G can be left disabled in BIOS as it's just a hint. CSM can be enabled too while GOP UEFI driver is also enabled.

I think the board I have is from MSI (somebody had thrown out case + board + CPU, which I salvaged out of interest 😅), but even though it had relatively recent updates (I think it went all the way to 2022), there was no BAR configuration. It was a pretty interesting process, first time I've patched modules into a BIOS/UEFI image.

I've never seen Windows 10 "renegotiate the BAR size" so if you can show this actually happens that would be great.

I hadn't heard about Windows (supposedly) being able to do this, before reading your Microsoft link:

On GPUs that support a resizable base address register (BAR), Windows will renegotiate the size of a GPU's BAR after firmware initialization in Windows Display Driver Model (WDDM) v2 and later.

 

[SayAgain]

I’ve heard others report 3090 shows a significant increase in FPS, but no data/video was provided. Perhaps ReBAR works better for older GPUs?

I‘ll get my side by side video up this week where I see no real difference in performance.

 

[_D_D]

I think the board I have is from MSI (somebody had thrown out case + board + CPU, which I salvaged out of interest 😅), but even though it had relatively recent updates (I think it went all the way to 2022), there was no BAR configuration. It was a pretty interesting process, first time I've patched modules into a BIOS/UEFI image.

Cool. Most stuff from X99 and even later had no BIOS resizable BAR setting. What the patch did was hook PCIe enumeration and changed the BAR size at that point using the capability pointer on the graphics card. That way the BIOS itself would assign the larger address range needed to accommodate it. By doing it POST BIOS requires reconfiguring PCIe bridge and graphic card addresses and setting Resizable BAR size as well as a couple of fix ups such as DSDT, MTRR's. Even with pure legacy BIOS, code can be placed into MBR sector and DSDT override used for Windows.

I’ve heard others report 3090 shows a significant increase in FPS, but no data/video was provided. Perhaps ReBAR works better for older GPUs?

Did some testing with Linux and a 3070 a while back. Total War Three Kingdoms showed a huge increase, I'd have to try and look back and check but something like an 80% increase. However the reason seemed to be the way things were handled with 256MB aperture as the increased FPS in Linux was still a little less than Windows with 256MB BAR results.

Another software that had been used for comparison was 3DMark PCIe BW but this shows clearly it is/was? bugged when Resizable BAR used if looked at closely.

Overall I'd have to say the nvidia Resizable BAR has been rather underwhelming from my own use.

 

[snemarch]

Cool. Most stuff from X99 and even later had no BIOS resizable BAR setting. What the patch did was hook PCIe enumeration and changed the BAR size at that point using the capability pointer on the graphics card. That way the BIOS itself would assign the larger address range needed to accommodate it. By doing it POST BIOS requires reconfiguring PCIe bridge and graphic card addresses and setting Resizable BAR size as well as a couple of fix ups such as DSDT, MTRR's. Even with pure legacy BIOS, code can be placed into MBR sector and DSDT override used for Windows.

Sounds right – and it's definitely cool that it's possible to do something like this. Not sure how hard it would be with a traditional BIOS, I think they had some sort of modularity as well? But for UEFI, the modular design makes it... I wouldn't exactly say easy, neither wrt. development or patching it in as an end-user. But it's definitely doable, and for the low-end Arc card I put in the system, it made the difference between graphics being a slugfest, to actually somewhat-decent game framerates.

I even think Secure Boot still worked? Should probably check up on that