CountMike :
No idea which system you are talking about but usual suspects are temperature and power delivery.
Agreed.
I use
https://www.msi.com/page/afterburner
I opened the program and clicked on the Gear(settings) icon. I then click on monitoring tab. I then click on System RAM(aka VRAM or graphics RAM). A checkmark appears. I then scroll down and click on Show in OSD. I do that over and over for each resource I want to monitor while I'm gaming. If I alt + tab out of the game to check on temperatures the load would immediately lessen and the temp. wouldn't mean diddly. After I have all the resources checked and OSD enabled I click on OK. Mike suggested temperature as a possible cause so that's a resource I will pay attention to. I grab a screenshot and post it here, using that Polaroid icon and an url ending with a jpg, bmp, png or other pic based extension
My CPU was at 48C and my GPU was at 66C. Nothing close to the thermal wall so thermal throttling isn't the issue.
He also mentioned voltages. I reset my PC and enter my BIOS and enter the Health Monitor section. I look to the 12V reading. That's the one that feeds the card. Look at your PSU and you will see +12V. That's the guy that feeds the GFX card. Within my BIOS I should see 12V or VERY close to that number. I should never see 11.** within my BIOS. That suggests a PSU issue. I just checked and it says 12.08V. I then enter Windows and I open
HwInfo and
HwMonitor. They show 12.08V and 12.07V. This means I can trust them and I know voltage isn't an issue.