http://bugs.winehq.org/show_bug.cgi?id=17648
--- Comment #1 from Sam skipsey aoanla@yahoo.com 2009-03-08 06:42:27 --- Note to add: with backbuffer offscreen rendering, there is no slowdown at all - the issue seems to be with the boss itself, which has a "transparent water, world-reflecting" effect.
This effect renders as black with fbo, and apparently correctly with backbuffer.