In a message dated 12/17/98 2:32:09 AM Pacific Standard Time,
shidel@ENG.USF.EDU writes:

<< is there any drawback to running a PIC at full steam ahead?  For instance,
 if I have a 20mHz capable processor, is it more prone to erronious
 readings at 20mHz? Or is the main reason for going slower for timing
 delays, as in doing a/d conversions?
  >>
Hi Scott!
I run all of our processors at full speed.  There are several reasons to use
other clock speeds. The first is cost and space.  4.00 mhz crystals are about
$1.50 to $2.00 bucks depending on size.  A TV color burst crystal (3.579mhz)
is about $0.69.  If my aplication is not timing critical then whay pay the
extra.
The second would be to facilitate an easy division to some desired frequency.
Some of the PIcs hav a built in UART for serial transmition.  The baud rates
are directly derived from the CPU clock frequency.  Picking values like
1.8432mhz makes baudrate generation simple and accurate.  Other frequencies
might get you close but with slight errors in the baudrate frequency.
If a part is rated at a specific frequency it should run at that frequency
without a problem.

Dave Duley
www.dreitek.com