Bryce5 is "relatively" lower in render times on windows. It is not a memory leak, nor is it an actual "setting" from within the render settings. My initial bryce4-b5 render was 14% difference. However, now that I have a bit of grip on Bryce 5 and its rather picky settings... I now have it to ~4% difference. I will be reviewing this necessary bryce setting and OS settings (yes it appears to be your OS!) that will reduce it significantly. Still waiting on other confirmations before I post this as fact, so thats why Im not telling what you need to do now. hopefully, in a day or so...I can give you better info. However, there is little need to experiment with Bryce settings in this matter if you are experiencing significant decreases in render time. In preliminary tests, it definately appears directly related to your machine and "background" behaviours of Bryce5. More soon! BT