We were puzzled but pleased with the results, but after receiving a tip from Michael Bean of AMUG, we rechecked the 17" MacBook Pro's X1600 GPU's core and memory speeds before, during and after running 3D Games using Graphiccelerator's "Show ATI Frequencies" function. Before starting a series of runs, the core measured 311MHz frequency. When we ran 3D games, it jumped to 423MHz. After sitting idle a few minutes, it fell back to 311MHz. We measured a similar jump in the GPU's memory clock from 297MHz to 450MHz. Now we know why the 17" MacBook Pro performed as well as the Intel iMac on the 3D Game tests.
