Here is a small benchmark that try to compare several optimized Intel OpenCV library functions with their GPU analogs, written using OpenGL and GLSL shader language.

More information HERE.

Because I can’t resist, here is my score (Core 2 Duo 6600 default clocks, Radeon HD 3870 Catalyst8.5, WinXP 32-bit) with Resolution multiplier set to 4:

------------ CPU  | GPU
step1:       75.3   21.5
step2:       35.8   22.5
step3:       05.7   00.7
Total Time: 116.9  345.3