pic oscillator question

[indie]

i'm working with pic16f84a with 20MHz x'tal on it, if i change the oscillator to 4 MHz x'tal (or anything less than 20 MHz x'tal) , what will happen??

 

[Exo]

everything will happen slower...

Program execution speed depends on the crystal, a pic does Fosc/4 inctructions every second (except branches wich take double the time).

So at 20Mhz a pic does 5000000 instructions /sec
A 4Mhz it does 1000000.

 

[Oznog]

Power consumption will drop to about 1/5th what it was before. You may need to change your fuse bit settings for the oscillator type, check your spec sheets.

 

[indie]

is there any different between analog oscillator with PIC oscillator??