I’d also recommend to use something else than msvcrt for the math stuff, but just by compiling it as optimized code would at least double the total execution speed, resolving a lot of slowdowns without any additional investment of effort on Bethesda’s side. They simply didn’t compile the code with the optimizing compiler switches. “They’d just have to add the string “/O2 /GL” to their Makefile. It could also be possible (but highly unlikely), that they ‘forgot’ to add the optimization switches to their compiler. After reading the entire thread, it seems that, most likely due to a bug somewhere, they decided to compile the game without optimizations (for example, it will use legacy x87 instructions instead of SSE2 or newer, etc).