Question In Multi-Gpu scenario, Primary GPU always performs better than secondary GPU

[sunilennaseril]

In my software, i have a functionality to playback of images. This playback needs to maintain 30 fps.

My machine has 2 AMD WX5100 GPUs with 2 monitors connected to each GPU.

When one of the monitor is made the “Make this my main display” from Control Panel\All Control Panel Items\Display, then this GPU becomes the primary GPU and the other GPU becomes the secondary GPU.

After this when i playback the images in both the monitors, the monitor connected to the primary GPU gets 30 fps playback, whereas the playback in the monitor connected to the secondary GPU gets only 24 fps.



Now if the main display setting is reversed, the performance will also be reversed.



Why is this performance difference based on the primary and secondary GPU. Please help.

 

[VirtualLarry]

Checked the monitor refresh rate under Display Properties , Advanced , Monitor in Win10?

 

[sunilennaseril]

Checked the monitor refresh rate under Display Properties , Advanced , Monitor in Win10?

Thanks for the quick reply @VirtualLarry
I checked the refresh rates now, unfortunately all monitors had the same 60 Hz

 

[davide445]

What's your motherboard?
In standard mobo the second PCIe slot does have lower bandwidth than the primary one (normally PCIe 3.1x4 instead of 3.1x16).
This result in most cases in a 5% drop in performances, but still
Edit: reading better your post: this cannot be the problem if the behavior is symmetric!

 

[sunilennaseril]

What's your motherboard?
In standard mobo the second PCIe slot does have lower bandwidth than the primary one (normally PCIe 3.1x4 instead of 3.1x16).
This result in most cases in a 5% drop in performances, but still
Edit: reading better your post: this cannot be the problem if the behavior is symmetric!

Yes i had checked the motherboard specs
https://www.dell.com/support/manual...b5135f-5063-4cc3-a667-c999fe06dc70&lang=en-us

I had used the slots marked [3] & [5] in the pic shown in above link

 

[davide445]

Yes i had checked the motherboard specs
https://www.dell.com/support/manual...b5135f-5063-4cc3-a667-c999fe06dc70&lang=en-us

I had used the slots marked [3] & [5] in the pic shown in above link

In the manual is written the mobo will have a single PCIe x16 using a Intel i7 CPU, or double if you are using i9 or Xeon.
What kind of cpu you have.

 

[sunilennaseril]

In the manual is written the mobo will have a single PCIe x16 using a Intel i7 CPU, or double if you are using i9 or Xeon.
What kind of cpu you have.

Mine is Xeon

 

[davide445]

Mine is Xeon

Ok I doubt PCIe is the problem.
It's a new PC and this was always the behavior or something was changed in his configuration?