Extreme perfomance drop with VSync on, Windows7 CUDA under performs with VSync on in windows 7.


I have a mini mac with Geforce 320M with windows 7. I have conneceted two displays to the mini mac, both showing the desktop.
I use CUDA to make some computation on the GPU, and I use DirectX9 to present images on the secondary screen(actually patterns for structured light). Because of the nature of the application, it is essential that I use VSync on with DirectX9 when displaying the patterns on the secondary screen(projector).
The issue is, when VSync is onm the CUDA calculations become extremly slow and under performing. When VSync is off, the GPU perfomes well and I get the desired FPS.
This is an issue I had for several months, the “solution” I found is to use Tesla which allows you to set TCC mode. Of course, not every platform will have Tesla. I wonder if I am missing something, because being unable to use both CUDA and VSync in DX means CUDA is not pracitcal for any Windows PC games.

Thank you,