Remember a laptop 5850 is not equal in performance to a 5850 in a desktop. It will perform more on the level of a 5750 or 5770.
Secondly turbo boos is only activated if fewer cores are used. So if an application uses only 1 core, it will overclock it to 2.9ghz, 2 core to 2.4ghz or something similar to that. If however a program uses all 4 cores, it will remain at it's default speed of 1.7ghz.