Dave VanHorn wrote:

> > How fast is a PIC???  My understanding is that the PIC's clock speed is
> > very under rated.  Has anybody had success at overclocking a PIC (
> > >20Mhz on 16CXX or >10Mhz on 16F84)?  If so, what frequency range,
> > operating temperature, exact part (including die shrink).  Is there any
> > charts or test results available (even if they are not blessed)?
> >
> > Todd.
>
> You realize of course that this kind of thing is only useful in hobby
> projects.
> Overclocking a micro in a commercial design, is a career-ending move.
> Or it will be, the first time you get a batch of chips that dosen't go as
> far beyond the specs as you'd like.

That depends on the application and the customer.  Is the customer aware of
the risks and are they willing to take them?  For example, a 16C74-04 PIC
will easily run at 20Mhz based apon my experience.  It is the same die for a
-04 and a -20.  My customer is aware and has accepted the risk of buying -04
parts and running them at max published die speed and it is not my
responsiblity as I specified the -20.  In the past 5 years they have never
had a problem.  I would question whether the testing is different or if it is
just the price.  The cost for the distributors to inventory all these
'different' flavors of the same part (die) has got to be more that the cost
of the fallout between a -04 and a -20.  Why not label all the parts at max
published die speed, cost reduce the products by inventory reduction, and
gain a marketing advantage over the competitors?  (This allocation would be a
good time to let the inventory on slow parts sell before switching to all
high speed parts.)

What I would consider overclocking a PIC is anything beyond the max published
die speed. In the case of the 16C74A this would be anything over 20Mhz and in
the case of the 16F84A it would be anything over 10Mhz.  So to clarify, any
clock rate over these speeds I would consider overclocking.  Futhermore,  I
fully agree with you that  to design a circuit using clocks greater than the
max published clock speed would be career suicide, but my curiousity still
asks: How fast can a PIC go beyond the specs.? (not that I'd ever run it at
that speed in a commercial design)

Todd