MSFS forums claiming 64GB of Ram helps on 3090s

[RXP 2,338]

3 minutes ago, Noel said:

Even my 2070 Super is able to maintain vsync to 30Hz w/ almost all settings at ultra almost all of the time

The problem is really specific to 3090 and VR though. The same systems with a 3090 in 3D are not exhibiting the same VRAM use patterns.

[Noel 4,503]

3 minutes ago, RXP said:

The problem is really specific to 3090 and VR though. The same systems with a 3090 in 3D are not exhibiting the same VRAM use patterns.

Yes I got that I was just having a side chat w/ Ixoye, thanks.

[Alpine Scenery 1,609]

10 minutes ago, RXP said:

The problem is really specific to 3090 and VR though. The same systems with a 3090 in 3D are not exhibiting the same VRAM use patterns.

It's interesting, I just wonder if there isn't some other reason causing it, no idea as I have no way to test that. Sorry, I'm just thinking like a programmer scratching my head because I mean we have a stack and a heap, and that has limitations on its own, but then when talking about memory buffering between the PC memory and VRAM, you have even more limitations. So it's limitations upon limitations. I just wonder how VR could be stable with someone for a lot less memory if you are seeing benefits from 32GB to 64GB, like where the issue would be.

Edited March 9, 2021 by Alpine Scenery

[Ixoye 1,821]

18 minutes ago, Noel said:

How is your 2080Ti running MSFS?  Even my 2070 Super is able to maintain vsync to 30Hz w/ almost all settings at ultra almost all of the time.  Seems like 11Gb for 3440x1440 should be pretty dang good enough no?

It running smooth and fine at 40-45 fps in max Ultra 3440x1440 , I really not need any faster card with my monitor, I have never seen it use more than about 9 mb V-ram.

Edited March 9, 2021 by Ixoye

[Ixoye 1,821]

16 minutes ago, Noel said:

 

dubble post

Edited March 9, 2021 by Ixoye

[RXP 2,338]

24 minutes ago, Alpine Scenery said:

because it is impossible to "quickly" load something large enough to be of any direct consequence when talking about this amount of memory. 

It depends. Any NVidia card can be loaded up really "quickly" because they do have dedicated silicon for copying the data from RAM to VRAM (and vice versa), which can run in parallel with the VRAM memory controller servicing the rendering at the same time. But if the game engine is coded in such a way the rendering engine is waiting for the data to be uploaded to VRAM because it is expecting it "right now" for the next frame, you'll stall CPU/GPU sync waiting for the data to be fully loaded. This is where it is possible this is affecting FS2020 VR with the 3090 because they'd upload much more data in advance. But in doing so, DX11 will also back this data up into RAM as well maintaining a copy. And again, this might well be just a NVidia driver bug with their DX11 driver implementation, where for example (and this wouldn't surprise me) they've tuned their algorithms at the driver level for 16GB (2^4 GB) and with 24GB the driver is hitting a corner bug case with their memory manager and controller. In fact the reasons could be multiple but there are external indications to me this is closely related:

- Most users with 3090 in VR are reporting much higher VRAM usage than you'd expect.

- Most of the same users are also reporting a higher amount of RAM used than expected.

- Most of them reporting trying 64GB instead 32GB are also reporting eliminating most stutters, hiccups, and have a much better and smoother experience.

- During VR beta and at VR release, I've documented how with the Index and SteamVR (the version at that time) Terrain LOD was causing much more stuttering. This and other correlated factors/settings lead me to think their rendering engine is stalling because they are massively updating their vertex buffers to a point it causes the CPU/GPU syncs. There was strong indications of this when using for example SteamVR frame timing tools and a few others.

- A few updates later they have managed to reduce some of the contention and SteamVR updates also did reduce the contention on the GPU so much that you could now raise for example Terrain LOD to higher values than before.

- With WU3 their are strong indications to me (again with different tools and cross checking settings against measures) they have introduced a more problematic bug again with updating vertex buffers, to the point it makes the experience in VR less good, and also in 3D the London PG is oversubscribing the VRAM in my test system 2070S even with modest FS2020 settings.

- They've told in a Q&A they were re-coding their mesh tesselator in order to exploit more of the multi-core. It is possible this alone is taxing the CPU because of a non-optimized task scheduler (I suspect they are just throwing UMS threads and not implementing a task scheduler sophisticated enough with features like work stealing, etc...) but this might also account for the performance problems experienced since WU3 if the introduction of such multi-threaded tesselator is also causing GPU sync/fence issues they didn't fully address.

These are just assumptions of course, but there are some issues in FS2020 I can relate to typical flaws found in coding game engines and these are not easy to solve either, but the main point selling me to the idea of lack of optimization in everything related to CPU/GPU and RAM/VRAM is when they say in a Q&A we shouldn't expect much more perf out of DX12, rather we should only expect more "visual" features. This means to me DX12 might not be implemented for what its best (the application gets fine control on VRAM allocation, buffers life cycle, finer GPU/GPU and CPU/GPU sync from multi-core), rather, the meaning of DX12 is using some of the new DX12U only features like DirectML (to implement something along the lines of DLSS2.1) and the use of Ray Tracing to reduce some of the path tracing workload in their rendering engine.

Edited March 9, 2021 by RXP

[Alpine Scenery 1,609]

22 minutes ago, RXP said:

It depends. Any NVidia card can be loaded up really "quickly" because they do have dedicated silicon for copying the data from RAM to VRAM (and vice versa), which can run in parallel with the VRAM memory controller servicing the rendering at the same time. But if the game engine is coded in such a way the rendering engine is waiting for the data to be uploaded to VRAM because it is expecting it "right now" for the next frame, you'll stall CPU/GPU sync waiting for the data to be fully loaded.

You could shift a lot of memory from the memory cache to the VRAM, but it would have had to already been loaded in the system memory, also the issue is it cannot be shifted quickly enough to actually be a significant part of the A to Z real-time rendering cycle, much of it has to be pre-loaded into VRAM before the shaders and everything else can be run and all things completed in the processing cycle. If you tried, it would cause a severe pop-in effect. There are algorithms that can cause huge amounts of wasted memory, but it's usually very obvious to spot and the first thing fixed before a game is released, because it will make lesser PC's crawl.

Edited March 9, 2021 by Alpine Scenery

[Virtual-Chris 682]

9 hours ago, Smartbomb said:

64GB G.SKILL TridentZ RGB Series 32GB (2 x 16GB) 288-Pin DDR4 SDRAM DDR4 3200 (PC4 25600) Desktop Memory Model F4-3200C14D-32GTZR

I could swear that this just said "32GB (2x16GB)" yesterday when I watched it...  When did you add the "64GB"? 

At any rate, as I said it looks good... but it would be interesting to get your assessment of 32 vs 64GB... a comparison video would be perfect.

Edited March 9, 2021 by Virtual-Chris

[Smartbomb 3]

18 hours ago, Virtual-Chris said:

I could swear that this just said "32GB (2x16GB)" yesterday when I watched it...  When did you add the "64GB"? 

At any rate, as I said it looks good... but it would be interesting to get your assessment of 32 vs 64GB... a comparison video would be perfect.

I did change it, just kidding 🙂 I can tell you this. Something changed with Sim update3 This in on a LOD 7

[Smartbomb 3]

On 3/9/2021 at 10:46 AM, RXP said:

And this is why despite any claim of "64GB is unnecessary" it makes sense when you're pushing data. Why? Because in this case, instead of having to stream smaller pieces of data as you fly along in order to discard farther geometry and bring new one to view and surrounding, the game can initially stream much more data from the get go to VRAM (meaning you have mesh loaded up as far as 100nm instead of 25nm) and as you go, it can stream same new data over a longer period of time because this new data won't be visible until much later. And this is the 2nd benefit: because the 24GB VRAM allow loading more data farther away, you can end up having enough data beyond visible reach, which means when updating new data it won't be needed right away for rendering and therefore won't make the rendering engine stall until the entire data is uploaded to VRAM (because it doesn't need this data for rendering the next frame).

I don't know if FS2020 is pushing the envelop this far but it might well be. Or they could have implemented VR as 2 separate render paths with duplicated data for example, which would explain why in VR, and maybe only in VR, you're consuming much more VRAM than expected. It makes sense because separate data prevents access contention for the rendering.

In any case, most users with a 3090 in VR are reporting higher VRAM usage than in 3D, be it a bug, an implementation feature, a DX11 issue, I don't know, but whenever you use VRAM with buffers in DX11, you can expect a copy of these buffers in RAM too and the more, the merrier in this case.

Something changed with sim update 3, I have seen my SDRAM usage rise dramatically It;s using 32GB and i've seen it go higher as of recently. This is on a terrain LOD 7 and Objects 2

[Ianrivaldosmith 5,317]

21 minutes ago, Smartbomb said:

terrain LOD 7

Isn’t that a stutter fest?

even with a 3090 and 5ghz cpu, anything above the slider of 100 is stutter inducing 

[Smartbomb 3]

3 minutes ago, Ianrivaldosmith said:

Isn’t that a stutter fest?

even with a 3090 and 5ghz cpu, anything above the slider of 100 is stutter inducing 

Not at all, It was a stutter fest anything above standard LOD 2 until I upgraded to 64Gb SDRAM. Up until sim update 3 I could fly through a LOD 9 terrain quite smoothly. My page file was huge with 32GB, 26GB page file. Currently I'm working through the bug introduced with World update 3 (it hit me with the sim update) causing 10fps and manipulators going off the scale. So far, cutting out the vfr map and not making any graphics changes during a flight has been going good.