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P50 - Docking station and sound stutter in games (DPC latency) - Solution!

P1/P50/P70 and later specific matters only
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athlon64
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Location: Split, Croatia

P50 - Docking station and sound stutter in games (DPC latency) - Solution!

#1 Post by athlon64 » Fri Oct 19, 2018 8:07 am

I just wanted to share the outcome of my problem finding process... which lasted quiet a while.

So if someone else has it this can help.

The machine is a thinkpad P50, M2000M, 6820HQ, 32GB/512GB - WIN 10 64 bit, all the latest updates.

The problem was that very often, when i played world of warships, after a while i would get really serious in game sound stuttering, together with some image microstuttering.



The cause of the stuttering was the fact that nvidia driver would have massive DPC latency spikes in game (8-10ms sometimes).

Which i confirmed with latencymonitor.

I of course first tried solving this by updating all the drivers and disabling many devices. Nothing helped.



In the end, after trying things out for weeks. I realise that the problem is the lenovo ultra dock. I only play games at home and when i'm at home my p50 is always docked. If i unplug the external display from the docking station and plug it directly into the P50's HDMI output. The DPC latency spikes stop and games run smooth with no sound stutter.



The thing is, i have replicated this on 3 different docks. Two lenovo ultra docks and one lenovo workstation dock. All of them have had their firmwares updated. And all of them caused exactly the same problem.



Yes, the problem happens no matter which one of the display outs on the dock i am currently using.



So if someone has an idea of how to solve this thing with the dock itself, that would be great.

Before that, i hope this helps someone else.

dr_st
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Re: P50 - Docking station and sound stutter in games (DPC latency) - Solution!

#2 Post by dr_st » Sat Oct 20, 2018 5:32 am

Yes, docking station compatibility problems are not as uncommon as one would think. These are more than simple passthrough devices.

Are you using the DP/HDMI for video and audio output, or video only (with the audio going through the analog connection)?

I would still investigate if there is anything more that can be done on the host (nVidia) side. About a year ago I was investigating an issue with USB headset frequently disconnecting when going through the dock hub, and in the end what solved it was a FW update on the headset itself.
Thinkpad 25 (20K7), X1 Carbon (20HQ), Yoga 14 (20FY), T430s (IPS FHD + Classic Keyboard), X220 4291-4BG, X61 7673-V2V
T60 2007-QPG, T42 2373-F7G, X32 (IPS Screen), A31p w/ Ultrabay Numpad, A21m 2628-GXU

athlon64
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Joined: Thu Feb 08, 2018 10:45 am
Location: Split, Croatia

Re: P50 - Docking station and sound stutter in games (DPC latency) - Solution!

#3 Post by athlon64 » Sun Oct 21, 2018 4:57 am

dr_st wrote:
Sat Oct 20, 2018 5:32 am
Yes, docking station compatibility problems are not as uncommon as one would think. These are more than simple passthrough devices.

Are you using the DP/HDMI for video and audio output, or video only (with the audio going through the analog connection)?

I would still investigate if there is anything more that can be done on the host (nVidia) side. About a year ago I was investigating an issue with USB headset frequently disconnecting when going through the dock hub, and in the end what solved it was a FW update on the headset itself.

No, the audio is going trough the analog 3.5 thinkpad output. If i use my focusrite 2i4 card i get the same result.
Because the problem has got nothing to do with audio. It's linked to the DPC latency spikes. Which are going to be caused by nvidia drivers when on docking station, even if i disable all audio devices.
Sound cracking is just the consequence of audio drivers waiting for the cpu to reply after their buffer has gotten empty. Because the nvidia driver is stalling the CPU for almost 10ms at the time.
That's what DPC latency measures.

You connect the display directly to any video output on the P50 and no problems happen.

This is probably a combination of nvidia drivers and the docking station. Maybe something can be done from the nvidia side but i can't conclude what.

dol
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Location: Dubai, United Arab Emirates

Re: P50 - Docking station and sound stutter in games (DPC latency) - Solution!

#4 Post by dol » Mon Oct 29, 2018 12:13 am

Based on your other post i would suspect there could be a glithch with your dock.
If you have a simple test case that triggers the issue I can try to replicate on my P50/dock.

CrazyTPFan
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Re: P50 - Docking station and sound stutter in games (DPC latency) - Solution!

#5 Post by CrazyTPFan » Tue Oct 30, 2018 6:38 pm

Like dr_st said it's either something driver related or it's something to do with the dock itself or maybe even the laptop.
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