SAM causing massive stutters

Warhammer 40,000: Darktide Performance Feedback
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I’ve done testing these past 5 or some odd hours and came to the conclusion that for my particular rig (AMD R7 3700x + RX 6700XT) it experiences consistent stuttering if SAM is enabled in the drivers.

For those that dont know, SAM is Smart Access Memory, which allows you to benefit from having Resizable Bar and 4G decoding enabled in the bios, granting the CPU access to more than 256MB VRAM.

Attempted Solutions:

Now, for the results, I didnt enable performance logging because I was dumb and forgot about doing it more than halfway through the testing. All results are with the majority of settings set to low with FSR 2 enabled on quality mode. and resolution set to 1440p, and portrait rendering as well as mesh rendering disabled due to their current and persistent issues. I was also able to perceive the stutters directly with AMD’s overlay that provides a handy dandy line graph for detecting microstutters (extremely useful tool to tell if any game is performing incorrectly.
So here they are.

Rebar enabled + SAM enabled + low textures = moderate and consistent stutters
Rebar enabled + SAM enabled + high textures = terrible stutters with large spikes on graph
Rebar enabled + SAM disabled + low textures = low to minor stutters, line graph nearly straight
Rebar enabled + SAM disabled + high textures = high amounts of stutter but nothing too severe
No Rebar + no SAM + low textures = insanely smooth gameplay, 0 stutter, line graph straight
No Rebar + no SAM + high textures = very very minor stutters, line graph almost completely straight

These results were tested in numerous matches, in fact the no rebar + no SAM as well as the Rebar + no SAM results was where I spent most of my time as I consistently stayed in matches to til the end because the game felt so damn good to play. The difference was was night and day where my 170hz panel was actually benefiting for once. While the Rebar + SAM enabled setting consistently made the game feel like I always playing on at 45hz even when it would show 80+fps, it felt so inconsistent and straining on my eyes.

Now these results can seriously vary, but one thing I noticed that stood out was the high texture setting, It always added a tiny bit or a lot of stuttering, even at high textures the game would never exceed 7500MB of VRAM (6700xt has 12GB). Also just to note, Resizable bar can vary significantly from CPU gen on gen, the 3xxx series tends to gain little or no benefit from it enabled while the 5xxx series or higher can tend to gain more, similar to newer 12th gen or higher intel CPU’s.

The strangest thing is the performance regression with SAM, when historically it has always been a “keep on” solution for AMD rigs, so this game is a outlier where it can severely hamper performance.

Platform:
[Steam

[PC] PC Specifications:
R7 3700x (stock)
RX 6700XT (minor 5% undervolt for cooling and consistently higher frequency)
32GB 3600MHz 2x16

If there are others with AMD rigs who could test with Rebar/SAM enabled or not, It would provide a huge benefit in seeing if this effects more AMD components, not just the 3xxx series of CPU’s and 6xxx series of GPU’s.

2 Likes
2

Hey, i’m on nvidia and since the hotfix (the 13# update was running flawless) my performance went downhill, and i have a good rig (4080,580xx3d,32gb ddr4 3200mhz, game on a NVME m.2 SSD).
In places where would surpass 200fps, im getting not only stutters, but 100fps and sometimes lower, dont matter the settings, and its consistely on places that are outside (cant remember the name, but its that one on the top, where the varlets talk about the sky protection being almost none).
I’ll try your stuff and see if i have any luck…

2 Likes
3

Good luck, in your case I’ve seen Nvidia have a hit or miss track record with whitelisting games that actually get regressions or vice versa. Though the last benchmark I saw for Nvidias rebar was from 2 years ago.
So fingers crossed in your case.

1 Like
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5800X3D
32gb DDR4 3000mhz
3060Ti

Rebar is yields abysmal results on this rig in this game: ~10-15% performance decrease.

If your board is an x570, you may check if there’s an 1.2.0.8 AGESA update available - it’s supposed to address some issues 1.2.0.7 had related to performance, but I seem to recall those “issues” were regarding the 5800x3d. regardless, may be worth diving into that. I’m on an x470 myself, no x.0.8 for me.

5

I’ll give it a shot, my latest bios was 1.2.0.7 from last year and I never got another since it was the most stable. If this works and I can reenable SAM/rebar for without suffering performance degradation it would much appreciated since Darktide is the only game that suffers a regression in performance from it.

Edit: updated to latest bios produced slightly better results with SAM on, but still not as smooth as with SAM off.

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Here my review so far:

My system:
Gigabyte B550 GAMING X V2
AMD Ryzen 9 5900X
16GB AMD RADEON RX 6800XT (current driver 23.9.1)
DDR4 PC3600 CORSAIR 16GB KIT (2x8GB) Vengeance RGB pro
SSD 1TB

After reading your post and an older one about SMT causing stutter):

  1. updated bios from F15a to F17C
  2. deactivated SMT in BIOS
  3. SAM stayed on (“Above 4G Decoding” and “Re-Size BAR Support” active)
  4. played one Mission on T5 Hi-In Special Gauntlet
    → already noticeble less stutter

then i deactivated SAM and played T5 Hi-In Sp-Gaunt on Hub Dreyko (most stutters and perf. issues were always on this map for me)
→ felt even smoother, only once did i have a really bad stutter, when someone left the mission.
FPS range was still 50-100 most of the time but it felt much more smooth without the stutters.

My ingame settings: 1920 x 1080 / no RayT / all high / no upscaling.

Overall it was such a huge increase in the gameplay experience, the fps drops are the same, the AMD/Win10 long loading problems also but the stuttering was mostly gone. I dont know what of my steps did contribute in what way but it feels now much better to play this game. Thank you guys for discovering this issues about SMT and SAM on AMD Systems.

2 Likes
7

disabling SAM absolutely worked. thanks

3080
5800x3d
x570 mobo

2 Likes
8

I tested with SAM on and off. I can easily say SAM off is better.
Ryzen 5600x
6700xt
2x16 3200 mhz Ram
1080p low settings

3 Likes
9

I cant thank you enough for providing this information. Built a new PC about a week ago, mainly so I can smoothly play Darktide as my older rig was 7 years old, and I had nothing but headache dealing with massive stuttering. Tried everything I could find, hardware and software wise but to no avail. Randomly came across your post and after disabling both rebar and SAM I finally get to play this game with no lag. 1% lows were single digits before, now they are yet to drop bellow 80. This needs to be addressed by fatshark asap, who knows how many people are hindered by this problem. Once again I thank you from the bottom of my heart.

Specs:
ryzen 7 7700x
MSI B650-P PRO WiFi AMD AM5 ATX Motherboard
7800xt
32ram ddr5 6000mhz

2 Likes
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I basically have the same specs as you except a 7600x instead.

I think I have rebar and sam enabled so you reckon to disable it? Im not sure if its just for this game but ive been getting nasty stutters in minecraft and satisfactory to name a few. Ima try this and see if it fixes the issue

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If you are having issues in other games as well it might be other reasons, like needing a bios update or something configured incorrectly.

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I’m using the latest AMD Preview Driver with AMD Fluid Motion Frames.
I’ve been waiting for that for a while now.
At first I was a bit disappointed that it introduced quite a bunch of stuttering.

But then I’ve seen this thread here.
So I tried disabling ReBar and SAM and it did in fact make it a bit better.
But not yet good enough for my taste.

Then I also disabled SMT (multithreading) since I read that this might cause problems with darktide.
Again, a bit better but not yet quite good enough.

So, I searched around a bit more and found this video:

At first I thought this is probably nonsense (and the difference definitely isn’t as big as the thumbnail claims).

You can skip most the video (it even says to activate SAM).
What is interesting is the registry stuff.
There is a download with a bunch of files.
Basically some registry changes and using a MSI tool to increased the priority of the GPU.
I don’t know if this tool works with a non-MSI mainboard.

But to my surprise this actually did something.
I can now play darktide completely smooth with Fluid Motion Frames.
And I just have 150-250 FPS most of the time. XD
Before using this setup with Fluid Motion Frames it was more like 80-120 FPS.

I have a spot in the hub where I usually test FPS.
On that spot it went up from pretty reliable solid 90 FPS to ~150 FPS.

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I dont ever test in the hub unless it’s in the psykanium as the hub can produce wildly different fps dependent on the players joining, which causes a hit to CPU performance as it loads in the new players data. Even some servers can cause a huge fps dip with nothing apparent causing it.
The main issue with the psykanium however is that it doesnt stress the CPU at all, in fact it doesnt represent the game at all in the stresses that a HI damnation stg can produce.

But I’ll take a look at vid and see if there are actual nuggets in there.

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So a bunch of that that video is either dubious or placebo, and frankly I dont think most normal pc gamers should ever be required to change to get a game working smoothly(especially when more demanding games can run so much smoother without issues under the same circumstances)

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And looking at the amount of settings currently in-game, I’m surprised by how backwards FS has gone considering there was a myriad of options available in Vermintide 2.

After all the time I’ve spent checking so many settings and round about methods of performance increases on a system surpassing their own recommended specs, the conclusion for fixing this games problems lies with FatShark themselves.

Again, I’ll keep running matches with the setting on and off to see if there is a disparity or just placebo. Heck maybe it was the 20th time reinstalling drivers and clearing cache that fixed it, who knows.
Edit: turns out it didnt change anything on my end and was just placebo, I am able to keep SAM enabled, which is always nice.
So It could be the combination of the latest preview driver with SAM just exaggerated any stuttering in darktide. I stil have to have settings to their lowest especially lighting and textures to avoid most stuttering.

1 Like
15

Did you try the registry stuff?
Because that’s essentially the only thing I changed that must’ve removed the stutters for me.

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No, my GPU never had issues with the lower power states to need to bother with it, it only really sees use in idle, which my PC rarely achieves anywho, so why would I bother for it to affect a game.

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The point is that this could affect other stuff that doesn’t seem connected.
I mean this whole thread exists because a feature that is supposedly improving performance causes stuttering. lol

18

This explains so much, I didn’t have issues in patch 13 while I was on my intel pc, but then I switched back to my AMD PC cause I wanted to increase ragdoll counts so I wanted more worker threads.
But then I started to hit these gigantic stutters occasionally, it’s really sad cause I didn’t have these issues on the AMD CPU machine before patch 13/14.

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