Istaria doesn't have a cap on the resources it can use, although as a 32 bit program it can't use more than ~3gb of memory at once. As for excessive use of cpu/lack of usage of gpu this is caused by mistakes on the part of the original development team of the game which we are working on rectifying. We're expecting performance to steadily increase with each technical update to the game's renderer (and we are making a lot of progress, fps is significantly higher than the past!)