TomD, this isn't an issue about the speed of computers (PC vs Mac), it's an issue about the speed of Bryce. I'm not talking about comparing the same scene file across platforms; I'm talking about comparing the same scene file on the same computer! The experiences reported in various places so far follow this pattern: Mac user renders Bryce4 scene in Bryce4, then renders same Bryce4 scene in Bryce5 for comparison. Scene renders significantly faster in Bryce5. PC user renders Bryce4 scene in Bryce4, then renders same Bryce4 scene in Bryce5 for comparison. Scene renders significantly slower in Bryce5.