As a purely for interest exercise, whilst at my last company, I played
with overclocking.

I was developing a device which inserted a pattern overlayed onto a
video signal, to indicate low battery in the video transitter.

Being an RF company, I was using an RF signal generator as an osc source
for the PIC at the time, and was running a 4MHz PIC 16F873.

I managed to get the thing going up at around 40MHz.

Interestingly, there were some gaps in the coverage. At about 24MHz, it
stopped, then picked upagain at around 26MHz, then there were a few more
gaps up the range.

The PIC was generating a flashing logo with the letters 'LB' in, and I
was able to get a fairly high resolution before the PIC gave up!


Regards, Kevin

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Michael Rigby-Jones
> Sent: 20 September 2002 08:06
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: Maximum frequency specs for pic inputs
>
>
> > -----Original Message-----
> > From: Mike P. [SMTP:mpoulton@mtptech.com]
> > Sent: Thursday, September 19, 2002 10:55 PM
> > To:   PICLIST@MITVMA.MIT.EDU
> > Subject:      Re: [PIC]: Maximum frequency specs for pic inputs
> > I got the impression he was looking for personal
> experiences of people
> > on the list, not numbers from Microchip.  Of course MC's
> not going to
> > say anything about it -- if they were, they would have put
> it in the
> > data sheet.  I would imagine that, amongst the vast
> readership of this
> > list, there are at least a few people who have overclocked some
> > PIC's.  I think he wants to hear from them.
> >
> The responses you have been given so far are typical of
> professional engineers.  They want to make products that are
> absolutely 100% reliable, and to do that you do not exceed
> the manufacturers specifications.
>
> As a purely "for interest" exercise then fine.  If you take a
> look at the archives I'm pretty sure that someone did post
> the results of "overclocking" a PIC some time ago (sorry,
> can't give a specific date, but over a year ago).  ISTR that
> they managed something over 30MHz from a 20MHz part.  You
> have to consider the implications of running the PIC this
> fast however. Timing issues, especially involving RMW
> problems will cause you no end of grief and are likely to be
> voltage/temperature sensitive.
>
> Regards
>
> Mike

__________________________________________________
Do You Yahoo!?
Everything you'll ever need on one web page
from News and Sport to Email and Music Charts
http://uk.my.yahoo.com

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics