CPU Bottleneck

[Chronictank]

Hi,
i know it has been prooven this bottleneck exists i was just wondering if someone could explain why this bottleneck occurs as i cant find any reasonable explanation using google.
I understand in the old days a cpu bottleneck would occur when you had a super fast graphics card and the cpu couldnt give it enough frames to render.
I cant see how this is the case nowdays as (for example), when running crysis my CPU bearly reaches over 60% so how could it be struggling to give enough frames? It very obviously is not having to do too much work per tick, so where is this bottleneck coming from?

Now the other way i see it is that there is a bandwidth limitation whereby the cpu i can only give so many frames and it has reached its roof, but this rationale falls down on the fact that if you increase the clock speed then the performance increases


Cheers in advance

 

[Chronictank]

surely everyoen wont have memory bandwidth limitations?
although more to the point if there was a bottleneck created by memory why does the graphic performance increase with an increase in clock speed

 

[Chronictank]

Ah that would make more sense (running 1:1 atm @ 357Mhz), so its not the fact you increase the cpu speed but because you increase the memory speed, is that correct?