I'm curious what other people are getting with Mavericks on this particular benchmark. First my machine is a Mac Pro 5,1 3.33Ghz Hex with Mac Edition GTX680. I am running the extreme preset Heaven 4 benchmark (1600x900 8xAA windowed), Cuda 5.47, Stock OSX drivers With Mountain Lion 10.8.5 I get the following FPS 54.8 Score 1380 Min/Max 9.5 99.4 With all versions of Mavericks I've tested (10.9.0, 9.1, 9.2) FPS 38.0 Score 957 Min/Max 7.6 94.5 What I don't understand is why Mavericks is so much slower for the average FPS versus Mountain Lion. If anyone has a similar system and Mavericks, it would be a help to me to compare scores. Is Mountain Lion just faster or Mavericks just slow on my system?