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I have 3 screens: 2 DVI via GPU and 1 DVI via the motherboard. Does anyone know if the video processing is in fact still happening on the GPU and being fed through the motherboard to my 3rd screen?

In the past I've noticed that I can drag a video that is playing from one screen to another and have never noticed any lag when I crossed the line that should split the stream between the CPU and GPU but I have never really contemplated why that would be happening, until tonight.

I recently started running BOINC again and tonight, while trying to watch Hulu, I started to see some lag in the video. I moved that Chrome window from the GPU screen to the MB screen but it still had the same lag. I then paused BOINC's GPU processing and the lag stopped immediately. Resuming BOINC's GPU processing brought the lag back. This is identical to the behavior that I see if the video is playing on a screen that is plugged in to the GPU.

I opened Task Manager and watched the CPU usage and then I paused and resumed BOINC GPU processing several times over about 5 minutes. While there was a spike when I toggled (up to ~80%) it always settled back down to ~50% usage within a couple seconds. The same spike happened when I resumed and when I paused so I assume that was just the BOINC manager toggling settings. Also, I did not stop CPU processing during this test, only GPU processing. I hope this is all the necessary info. Thanks for your time.

My rig:

  • Windows 8.0 Pro

  • Core i7-2600 3.4Ghz

  • EVGA GeForce GTX 550 Ti 1GB

  • 16 GB DDR3 12800 RAM

  • ASUS P8B75-M motherboard

  • In a system like yours only the dedecated GPU should be used unless you specifically choose to use the other GPU. It also won't seamlessly switch between the two that requires drivers that support doing that and you don't have them installed. – Ramhound Mar 26 '14 at 17:50
  • I had to manually re-enable the DVI port that's on the MB via the BIOS since the GPU being present disabled it. If that's what you mean by "unless you specifically choose to use the other GPU" – user310768 Mar 30 '14 at 3:26
  • That wasn't really my question though. My question is why do intense GPU processing apps seem to affect video playing from both the GPU and IGP. – user310768 Mar 30 '14 at 3:28

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