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I've recently bought a second GPU for Vegas Pro (Rendering) and for better overall performance while gaming.

My Rig:

  • i7-4790k OC 4,7GHz watercooled
  • 32GB DDR3 2133MHz
  • a bunch of SSDs and HDDs
  • 980 Strix OC
  • my new RX580 Nitro+
  • Windows 7 Pro x64

I figured I could run two seperate GPUs individually for each monitor. That way my second monitor shouldn't cause dropped framerate while gaming. Also I wanted a card for OpenCL (Vegas Pro), so I picked up an RX580.

I've noticed very strange dips in performance though. Sometimes everything is fine. Both run at their respective framerates. Suddenly my main monitor (980) drops by about 20 fps for no reason and stays that way. When I play a Youtube video on my secondary monitor and play certain games, I get 15-20 fps. What could be the issue here?

The drivers? AMD drivers and NVIDIA drivers not understanding each other? The CPU bottlenecking because it has to talk with both drivers simultaneously? A driver that's not fully worked out for the RX 580 yet?

I'm curious for your opinions.

Edit01: One thing I also should mention: I'm running an Asus Z97-WS board. That particular MB has 16 PCIe lanes + 16 via some extender chip. Might that be an issue? Is it using those lanes for the GPU and hence the performance issues?

  • In similar scenarios, most of the time it was the nV driver's components at fault. Yes, the drivers don't really go to well with each other. What versions of drivers you currently use for both cards ? For the RX580 you could try the Crimson Relive 17.5.1 beta,as for the nV card I can check later on what version I use (which is pretty good, I think it was 376.33, but will double check). – Overmind May 5 '17 at 9:41
  • I should be using the latest version in both cases right now. I had to revert to an older one previously, because hdmi audio to my TV didn't work with the new driver, but they fixed that in an update. Thanks, I'll try the beta driver then. – Thomas Huber May 5 '17 at 9:42
  • For nV 381.89 also acts pretty good for dual setups but I did not test it on long-term. 382.05 I rate as inconclusive atm. – Overmind May 5 '17 at 9:44
  • 381.89 is the one I was using. I upgraded to the latest one, the TV audio issues came back and I had to revert back to 381.89. – Thomas Huber May 8 '17 at 11:43
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For those curious: I'm pretty sure I've found the cause and a kind-of solution for it.

The Asus Z97-WS has the 16 PCIe lanes from my i7-4790k. But the extender chip also "has 16 PCIe lanes". What it does, is take the real 16 lanes and switch them between the two gpus.

I went into the BIOS and set my secondary GPU to Gen3 x8, so it basically switches half as often. Some might say, just set both GPUs to x8 and you're good. I chose to have my primary run at x16 and the secondary just cutting in here and there, because it either is used only for rendering or occasional watching of YouTube videos.

This might not apply to a lot of people as it is a 300+$ board, but you never know.

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