Yeah quad core, not sure on the hyper-threading.

Ended up just scaling down to 100 x 100 in PS. Still took 20 minutes though. CPU usage only spikes higher for the last maybe 20 seconds after it finishes the generating mesh task.

Thanks though.
100x100 turned out fine anyway.

256x256 bmp taking 45 minutes to finish. Activity monitor shows Sketchup only using 5% while this is processing.