Here is something I have been doing with the 73.

Given that an interupt can occur at any given time, and code execution could
be taking place on any page and working with any bank.
What does this mean?

I had found like many others that things with a PIC are not nicely restored
with a RETI.
So we all do the status and w thing, no big deal.  But what about rp0 (bank)
and pclath.3 (page)?

Well, the first thing you do in your ISR is clear rp0, now you are safe to
do the status and w thing.  But how do you know what  rp0 was before you
cleared it?  I have heard said, "you can duplicate _copy FR in both banks",
yuck, and I am tight on space.  What else can I do?

Hey, hold on a sec. my ISR seems like it is all over the place some times.
I know I have code in page 1 and that the pclath is adjusted appropriately
for calls, lookups etc.  This definetly can cause problems executing my ISR
in page 0.  Hmm, now it looks like I need to record and restore pclath as
well.  Now things are looking ugly.

I need a FR that can be addressed from either bank.  That is where I will
store rp0 and pclath.3.

Well, this is how I have been doing it.  I use the status register, bits
7and 6.

Any comments welcomed, good/bad, does this help anyone?
**********************************************************************

;bank = status.7  ;general purpose bit 0=bank 0, 1=bank 1
;page = status.6
 ORG 00H
 jmp begin
 org 04h

:loop clrb gie          ;turn off int.
 jb gie,                     :loop

 snb rp0
 setb bank                                                ;*Recording the
status of rp0
 clrb rp0                  ;set bank 0               ;*Make sure that you
are accessing the right bank

 mov w_copy,w                                        ;*Doing the status and
w thing
 mov s_copy,status

 snb pclath.3
 setb page                                               ;*Recording the
status of pclath
 clrb pclath.3                                            ;*Make sure that
you are accessing the right page

 <Work your magic here>

 mov status,s_copy
 swap w_copy
 mov w,<>w_copy

 snb page
 setb pclath.3                                            ;restore page

 snb bank
 setb rp0                                                   ;restore bank

 clrb bank                                                 ;reset bank flag
DO NOT FORGET
 clrb page                                                 ;reset page flag

 reti
**********************************************************************

Take care  -jim