Cheat Engine comes with a feature called speed hack which basically can slow down or increase speed of the game. Actually, not only games, if there is a software with clock ticking it can speed-en up that too. How does that work? I might imagine there is some internal clock on which these things run but not sure how these things happen on low level.
While this feature has worked on most of the games I tried, it has also failed on many, for eg, NFS Most wanted. Why? Is there any different mechanism on which these games run or it is just some anti-cheat?
Cheat Engines Old Speedhack:
Cheat Engines New Speedhack:
Detection:
Source: http://wiki.cheatengine.org/index.php?title=Cheat_Engine:Internals#Speedhack