It depends on the motherboard. If it supports faster memory, it'll work fine.
I have two questions:
1. If I have a 1600 FSB motherboard then a 1866MHz or more speed rams will work at 1600MHz i.e at max FSB of motherboard. right??
2. Peripherals connected to north bridge or FSB of motherboard can not work with a speed which is more than motherbords's max FSB. On that case the peripheral will be downclocked. right??