Hello, I have an Ivy Bridge desktop running a clean Windows 7, which I use to test the HD4000 with OpenCL. My application is a software h264 encoder multi thread. For now it only uses the CPU. The thing is the test application has a big variation in performance, for different tests with the same configuration. Whereas it is pretty much stable when I run exactly the same thing on my Sandy Bridge desktop. I tried to disable turbo mode and power management to make the frequency stable but it changes nothing. I have no other processes running in parallel (no more than on the sandy bridge). I look at the I/O while the app is running and there is nothing different from the sandy bridge. (The source file to encode is stored onto the RAM memory). That's why I am wondering which parameter could affect the performance that much, and how to solve this problem. The variation is about 10% in encoding time per frame, or even more. Thank you, Chris