I have created a very simple fractal generator using brook+, because i am stuck with hd 3870. However the results were surprising as 3870 turned out to be 5-20 times faster than my dual core cpu (intel 6400) depending the resolution settings etc. Note that 3870 used an unoptimized kernel and that the cpu used 2 threads.
You can download my program here: http://depositfiles.com/files/llys7tzdz
(If anyone wants to help me to optimize the kernel i would be gratefull as i am new to gpgpu)
In order to build it and use it, you will need glut32.dll on system32 folder, visual c++ ati stream sdk v1.4 of cource and some other opengl libraries installed in your microsoft sdk folder.
It supports real time panning and zooming even with 3870.
Use + and - for zooming, the arrows for panning and < and > to change the iterations.
If anyone wants to see the source or the executable let me know
You can use the code if you want, don't ask for permision