Not sure about that, once i have read a report about PIC32 overclocking and the person was able to make it run at 100Mhz (MAX is 80MHZ). But it is kind stupid because a uCU is not as a homeprocessor. You overclock you processor at home because they are expensive and you dont want to buy a better one. For uCU it is not a good reason as you probably is going to loose reliability.