Measuring GPU Performance
How are you gauging your GPU usage? If you are only using TestMaxSpeed, then that is problem #1. Rhino’s display is a passive frame display, not an active one. Rhino does not try to generate constant frame rates at all times (like a computer game does). It draws a single frame, ends and exits.
Trying to determine overall GPU usage on a single frame would be like trying to determine how fast your car’s top speed is by measuring how fast it takes it to move one inch from at rest position, and then extrapolating that into miles per hour. Not a good approach to finding the best answer.
A better way (but still only an approximation) is to use the Rhino’s TurnTable command. Turntable does try to maintain constant frames, and most GPU monitoring tools can then post better results. There is a Hollomark for specifically V6 and V7, which can be found on the Rhino support forum.