I can't believe that at 10 MHz (or so) changing
trace width will have that much effect - BUT,
how near or on the edge might a critical circuit
parameter be for a particular design and layout
and where an apparent change of trace width
has en effect - that is the $64K US question.
Designs as critical as that are to be SERIOUSLY
avoided.

I would look elsewhere for that magical, critical
factor makes or breaks 'the deal' ...

How desirable in some of these designs would a
simple external oscillator comprised of three
resistors, a couple of caps (value 39 to 120 pF)
and a single cheap bipolar NPN transistor plus
crystal be *in return for* oscillator reliability?

Some serious bench work needs to be done
with a couple of these PICs and detemine
whether these built-in 'osc' elements require
more (or less) bias to put them into a linear
operating region, whether the xtals are suitable
or not, etc ... Some simple adjustment on cap
parms (the two external shunt caps) I would
think would solve most of the 'incompatibility'
of all but the most stubborn of crystals.

My .02 US anyway ...

Jim P


----- Original Message -----
From: Dan Michaels <oricom@LYNX.SNI.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, June 10, 2000 4:56 PM
Subject: Re: [PIC]: XTAL startup issues on PIC 73B


Jim P wrote:
>The simplistic approach of utilizing a single 'inverter'
>stage to be used as a crystal oscillator has always
>been bad design practice in the past and is always
>fraught with it's own set of perils.
.........
>
>I don't know what MChip (or others) actually has
>fabricated on the die as an 'oscillator' stage but it
>probably isn't a well designed analog 'oscillator'
>stage with suitable feedback or biasing.
>
>The moral of the story: It's "potluck" with the
>onboard oscillator and an external crystal all of
>unknown specification.
>

OK, I hear what you are saying about the single inverter stage
oscillator. OTOH, there are how many BILLIONS of these things
out there? Can they really be so fragile that simply changing trace
width like Harold did is gonna have such a great effect?

Cheers,
- Dan Michaels
==============