Issue with videocard performance

Hello, I am not sure if this question has been asked before, I did a quick search and did not find anything. My issue is that I get better performance without a video card then I do with one and I am curious as to why. With the video card n64, ds, ps1 games are playable but have massive slowdowns in certain areas, without the card everything is pretty much playable. Any thoughts?

My processor: Amd APU a6 3600 Videocard: Nnvidia gt 560

My guess is that it’s due to AMD’s open source driver being waaaay better than the open source nouveau driver.