OK. But possibly it's being disabled by your driver when you run the application?
It shouldn't be. Especially when ran in windowed mode. I also tried full screen and full screen with display resolution set to the room. In all cases the same result. But as I said, I got this problem with another, totally unrelated PC. Different hardware, clean install etc. So it must be larger than that. Maybe I will try my laptop with AMD later and see if has the same problem.
edit: After a quick profiling I found the problem is setting the room_speed large. The room_speed = 1000 makes the whole thing CPU bound. Even when vsync is on and only 60FPS is possible. But the bound is actually a lot lower than that. At room_speed 59 I get 3% CPU load, at room_speed 60 I get 25%.
edit2: With vsync off I get 0-3% load even with 60FPS. Or 500fps for that matter. But 600FPS again give 25% load. I think the CPU bottlenecks when I make it draw more than I can actually draw. Maybe the opposite, it bottlenecks when I ask for I/O while I can draw a lot faster. Anyway, we should multithread ENIGMA at least partially, so I/O is one thread drawing another.