The order of results are more or less would I would have guessed. The difference in B and C is probably due to the Q6600. A quad core CPU, a 64 bit OS and a 64 bit renderer should be faster at a given clock speed than a Duo core, all other things being equal. The difference in clock speed of 2.5GHZ over 2.4GHZ is not enough to make the Duo core machine as fast or faster than the Q6600. The 75% increase over using the 32 bit OS is interesting. I'll have to look at going to a 64 bit OS again I guess. Thanks for doing this little comparison.