>
> I need to run a PIC16F84 on 4.194304 MHz (2^22 hz) for some precision
> timing, and since this clock speed is a multiple of 1024, it works
> extremely well with the Timer0 module on the PIC. Question is, would it
> hurt to run a 4Mhz PIC at this speed, or should I rather opt for a 10Mhz
> PIC?

All F84's come off the same wafer and are tested for speed performance.
An -04 is one that doesn't meet -10 specs, it may even run at 9.5MHz,
but not 10MHz. I've an -04 that's quite happy at 7.3MHz. You can't
GUARANTEE that an -04 will run at 4.2MHz but it probably will. If this
is a one-off I'd say try it but for a production run you'd be safer
using -10 devices, unless you want to test each -04 as it goes into
service. Most of them would pass I think, the 4.2MHz being so close to
the nominal 4MHz grading. In a sense you aren't overclocking, the -04's
just have a possible operating range of 4 to 10 MHz.