Question / Help 980GTX VRAM downclocking when recording

Nik Dan

New Member
Hello,

I am a new user of OBS, switching to it when Geforce Experience Shadowplay started requiring a registration to use, cause #@!@ that. I am using OBS Studio 0.15.2 64-bit.

My System Specs: Intel i5-4960K@4.4Ghz, Gigabyte Z97X-SLI, 16GB Corsair DDR3-2400, EVGA 980GTX SC with latest 368.81 drivers, Seasonic G-650W, 1x Crucial MX500 240GB SSD, 1x WD Caviar Black 1TB HDD, 1x 4TB WD Green HDD, Soundblaster Z, LG IPS 1080p monitor, Blue Snowball mic, Windows 10 Home 64-bit.

I watched a couple of tutorials and I was soon happily recording with my commentary at 1080p@60fps, using NVENC, seemingly without any issues. But when I tried a couple of more demanding games, I noticed a 10-15% decrease in framerates when recording, which is not supposed to happen.

Investigating with MSI Afterburner and GPU-Z, the mystery was soon solved - for some reason when recording, my GPU's memory frequency drops from 3500Mhz (7000 effective) to 3000Mhz (6000 effective). It is a pretty massive drop, having a visible impact on performance, at least on demanding games. Core frequency is not affected, boosted to about 1350Mhz.

The drop happens the very second I use the "start recording" hotkey (I assigned the asterisk * key), and the frequency is restored the very second I stop recording. It has nothing to do with GPU temps which remain in the low 70s, or PSU stability which is rock solid.

The problem remains when recording at a different resolution/framerate, and across different sources (Display, Game, Window Capture).

I relented and returned to Shadowplay, which as it turns out does NOT have this weird problem. But I liked OBS more, especially its mic noise gate filter that made my recordings much clearer, and I would like to return to it.

Is this a bug? Or am I being dense and have simply screwed up something obvious in the OBS settings (not according to the tutorials I saw, but it's not like they were made by university professors).

Thank you for your time.
 

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Suslik V

Active Member
NVENC causes GPU memory to downclock Same?

There was an answer:
Got a reply from an Nvidia Rep ManuelG.

"CUDA is used in NVFBC. Because many of the use cases where an application uses CUDA, precision has a higher priority over speed. This is part of the reason why workstation CPUs and GPUs typically run at a lower clock speed than their consumer equivalents. We are developing an app profile system to catch cases where CUDA is used for consumer level applications (such as OBS) so that the memory clock speed will not clock."
 

Nik Dan

New Member
Thank you for your reply. Yes, it is the same issue. It's been a year and a half and it seems to be unresolved :(. I wonder if there is a workaround...
 
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