CPU faster and less laggy then GPUs

So my system specs to begin with are these: http://es.pcpartpicker.com/p/hcRGYJ

I have SLI enabled.

Ive tried using my GPUs for rendering, so i set up all the setting i know of towards GPU rendering as you can see here:

When i start to render a 3,5M triangles scene at [email protected]% 300 Samples, 256x256, my pc starts lagging and it didnt finish to render 2/60 in 5 minutes.

When i then set it to CPU with all 8 threads, same settings but 16x16, it renders in 2:30 minutes without any lagg at all.

Are there any settings im missing?

i tried googling, but everything seemed as old as gtx 500.

Also to add, the render is a simple clay render, no material, one camera and a [email protected]

This will not solve your lag problem, but enabling SLI is AFAIK bad, bad, bad for GPU rendering. GPU rendering will use all of your GPUs regardless, but SLI seems to create so much overhead, that you might see up to 50% performance loss (or so I’ve read).

However, the laggy interface issue might only be solvable by using a third, dedicated GPU not used for rendering but just for viewport display.

ill try without SLI then.

Alright, it works great without SLI now, and i didnt encounter any lagg either, so thats good. the viewport render worked kind of with SLI, and it feels a bit faster too.

Are you suggesting that 1 GPU is ok and 2 or more get slower? Am I missing something?

Only if they are in SLI mode

ah ok, so it’s just useless to have a SLI-capable motherboard.

Only if you’re just using it for Blender