Maximising clock speeds

Just a short note on chrystals, clocks and instructions. On the PIC24 and PIC32 you have very high maximum MIPS, million instructions per second, counts. To reach these speeds, you should not use an extremely fast chrystal. Instead, you use what is called a PLL, phase locked loop module that is found within the mcu. This expects an input clock of between 4 and 5MHz, but multiplies this to get a much higher internal frequency. You may use a faster external chrystal, but this has to be divided down to be in the interval that the PLL expects by a prescaler (also found in the mcu).