>         Is it possible to do serial I/O with a PIC16c84 clocked at 4MHz?
> I'd perfer 19200/38400 or a variable speed, where can I get information
> or routines for doing this?

Nearly anything is possible.  As to what's practical...

By far, the easiest way of doing serial I/O is with dedicated polling
routines.  Such routines will do nothing except either output a character
or input a character (the input character routine will wait until either
it receives a character or times out).  Polled I/O is half-duplex only,
and may severely impact the rest of the system (e.g. everything stops when
the input routine is waiting for a character)  On the other hand, it's
simple to code and can go extremely fast (even 115,200 would be no problem
for a 4MHz PIC).

The other approach to handling serial I/O is to use a routine which gets
called at the baud rate (for transmit) or at three times the baud rate
(for serial) and handles the outgoing/incoming data.  Such a routine may
be implemented very nicely as a state machine, though I don't have any
code handy to post.