AFAIK, the speed rating of the non-windowed PIC's is simply a reflection of
the mode they were tested in.  An 04 part will probably run OK at 20MHz, if
the config bits are not already set (being an OTP you can't change them if
they are), but Microchip will not want to hear if they don't operate at a
higher than rated speed.

CIAO - Martin R. Green
elimar@bigfoot.com

----------
From:   Bob Blick[SMTP:bblick@TELIS.ORG]
Sent:   Thursday, September 25, 1997 2:04 PM
To:     PICLIST@mitvma.mit.edu
Subject:        HS fuses in 04 versions

Are the fuses the same in the 16C71-04 as the 16C71-20, as regards the
oscillator? In other words, even though it's only a 4 MHz part, can the
oscillator be run in HS mode? I know it uses more current in that mode, I
just need to know if the fuses are physically there, and if the chips are
functionally equal except for speed rating.

Thanks,

Bob