It can't be hardware, as others have noted these kinds of games have been working great on machines that are magnitudes slower than the OPs machine. Maybe it's some kind of search that is running linearly on an assumed small dataset and it gets bigger than imagined, instead of it running a binary search or something. Maybe some of the data is unreasonably large for what it contains and can't get cached as easily.

And, as others have mentioned, if you really want to know, profile.