I know this is a random question and sounds rather strange but here's the situation I've just discovered: I'm running a simulation on my mac pro. Each output timestep takes about 15 seconds to complete. I've just tried the exact same run on my MacBook Pro and each output timestep takes about 10 seconds. My Mac Pro is a 2.66GHz Quad Core 2006 Mac Pro with 4GB RAM currently running at 2.9GHz. My MacBook Pro is a 2.53GHz Late 2008 (Unibody) MacBook Pro with 4GB RAM. It seems a little odd to me. This is a single threaded task so the fact that one's quad core and one's dual core shouldn't make any difference. As far as I can tell, both the chips are Core 2 Duo based. My only thoughts are that maybe the FBDIMMs vs DDR3 are holding up the Mac Pro, still seems strange though. Its not very memory hungry at all - just over 4MB real Memory, 2.6GB Virtual Memory according to the Activity Monitor.