Interesting. With the FirePro V5700 (Rv7x0 chip), I measured 8 bit effective LUT bit depth (while it's able to send out 10-bit from the framebuffers?). With my HD5850 (Evergrenn chip, which can't -officially- send out 10-bit from the framebuffers), I always measured 10-bit, even with DVI attached 8 bit (or 6+2 bit) displays (because it applies some kind of dithering for the LUT output when it's connected to 8 bit devices...) So, any pre-Evergreen FirePro user should think about this "profile only" thing.