GeForce 8600 GT vs Intel Core 2 Duo 2.45Ghz Who is stronger?

I’m executed on GPU and CPU one simple algorithm. Iterations from 0 to 60 000 on three threads on GPU and three sequential cycles on CPU.
As result i have GPU execution time 4…milliseconds and CPU - 0.56 milliseconds.
Why GPU time is greater than CPU???

A GPU needs thousands (like 10000 or more) threads.

thanks! In another example at 500 threads it is really worked faster than CPU :-D