On Thu, 18 Jun 1998, Will MacGregor wrote:

> > Is there presently anyway I can get a Pic16c54 or any other Pic for that
> > matter to be able to execute code at 1 nanosecond per instruction?
> > If not possible with Pics are there any other microcontrollers that can
> > execute instructions this fast? Thanx in advance for for responding.
>
> This would correspond to a clock speed of 4GHz (billion cycles per second),
> since all PICs require 4 clock cycles for each instruction cycle.  To the
> best of my knowledge, there is no microprocessor on earth that would clock
> that fast.
>
> The fastest PICs are rated at a maximum external clock frequency of 33MHz,
> or 121ns instruction cycle time.
>


> All PICs can operate on an internal RC oscillator which has a fixed nominal
> value of 4MHz, or 1 usec instruction cycle time.
>

Will, unless there is something major that I have missed on the PIC
datasheets, this is only true on a few of the PICs, like the 12C508/509.
Most of the PICs require an external R and C for RC osc. mode. You could
run it with just the R and use the pin capacitance and the board
capacitance for the C,
but it would be very unstable and vary _GREATLY_ from device to device.


Sean

> Hope this helps
> Will MacGregor
> Software Design Engineer
> Newbridge Networks Corp.
> tel: 613 738-2434
> fax: 613 739-8267
>