i5 vs i7 question

[Jaycen12345]

http://
in digital foundry video, at the beginning
pentium, i3, i5, i7 all perform similarly paired with a titan x
However, in 2:00 of the video, pentium, i3, i5's framerate all started to drop except i7
why is that? is this bottlenecking?

 

[Mr Kagouris]

That's because the area near the end is much fuller and the CPU has to do more things, so the framerate drops with weaker CPUs.

 

[Jaycen12345]

That's because the area near the end is much fuller and the CPU has to do more things, so the framerate drops with weaker CPUs.

so does it consider as bottleneck then?

 

[Mr Kagouris]

More or less.