The X1600 is probably one of the worst supported cards for OpenGL on Windows, and it's not all that great hardware either, which is probably why Apple ditched them almost immediately for NVIDIA in their MacBooks. I'm afraid the outlook is grim in this situation. MacBook Pro with ATI X1600 graphics under Bootcamp Parallels Desktop is staggering a few steps behind Fusion and bringing up the rear.
On my MacBook Pro, Rhino performance is an order of magnitude better. Then you have access to all your RAM, all your processor cores, and access to the accelerated hardware provided by your graphics chip.
Still, neither can hold a candle to the performance of rebooting to the Bootcamp partition and running Windows directly.
