Many games utilize 100% CPU usage even when they don't need that much. For example, I run a game with DOSBox at 2500 cycles, DOSBox utilizes less 30% CPU, and the game seems to run at full speed, but as soon as I increase the cycles, the CPU usage goes up. When I run it in real DOS or in a Windows DOS box, the game also utilizes 100% CPU usage. The same goes for Windows games as well, it seems to always utilize 100% CPU to avoid writing extra code to handle correct timing. This even happens in some educational games that only use pre-rendered graphics!