Newsgroups: comp.robotics
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From: seeker@indirect.com (Stan Eker)
Subject: Re: clock-doubling on 68hc11Ax
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Date: Sun, 16 Apr 1995 00:29:52 GMT
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Brian Olson (olsonb@LAHS.LosAlamos.K12.nm.us) wrote:
: I've heard from many places including Motorola that the only thing 
: preventing the HC11's from running faster is temperature.  On the HC11 
: and E9, Moto says that bus speed can be 3.0MHZ (XTAL of 12MHZ) when the 
: temperature is less than 85 degrees C.  
: 	Don't take my word for it, but if you keep it really cool, it 
: should be able to do double the normal rate.  Definately look into PLCC 
: heatsinks and itty-bitty fans.

: \ /~~~~~~\       Brian Olson
:  X DARWIN >      olsonb@lahs.losalamos.k12.nm.us
: / \______/
:    L    L


: On 12 Apr 1995, Quantum Flux wrote:

: >     Is there a danger in doubling what would normally be an 8mHz clock to 
: > a 16mHz on a botboard using the A series 68hc11? Would the board just 
: > fail because the CPU would not handle it? I also have a 68hc11Ex chip (9 
: > I think) -- would that chip fail as well?
: > 
: > Adam

If you can keep it cool enough, try it.  You *might* be able to get a 2MHz
part to run at 4MHz, but it's MUCH more likely to work with one of the
faster 3MHz parts they make.  Most chips don't skew very well at over 150%
of the maximum clock rate, but it's extremely rare that you'll have a
handful of smoke, plastic and sand.  They're only a few bucks each, so give
it a shot and post the results!  I'm interested, too.  I've overclocked
8051s and run 'em at lower voltage, but never tried the 68HC11 stuff (yet).

