Well, there is no Bryce 7.5, it stopped at 7.1. With Bryce 6.0 file compression was introduced - a bad move because compressing/decompressing is done in memory. Memory limit is still 2 GB (though that can be extended if there's enough memory in the system) but it can use up to 8 CPU cores to render, which speeds up things considerably. I still have all versions from 4 up installed but use the older versions seldom, 7.1 is very much improved.