Exactly how many clocks does a Computer consists of and how do they synchronize with each other?
Modern processors tend to have more clocks than processors in the past, because that means when a part of the processor isn't used, it may be possible to switch off that part completely, including the clock, to save energy. 

Clocks are often not synchronised, because synchronising and keeping them synchronised is expensive and complicated, and if you can make a part of the processor work correctly without synchronising its clock, that's overall cheaper.