|Does anyone have a simple way of deciding what OSC CAL value to use for
|508 JW parts, I have two and had problems with the programmer, and now
|don't know what the value should be for these devices.

Your best bet would be to program in a little test program which sets the calibr
ation to
a certain value and then see how fast the parts actually run.  I'd suggest somet
hing like:

000..1F7 left blank
1F8  movlw  $7F
1F9  xorlw  $FF
1FA  movwf  PORTA
1FB  movlw  $FE
1FC  tris   PORTB
1FD  movlw  1
1FE  xorwf  PORTB

1FF left unprogrammed

This should cause pin GP0.0 to change states once every 512 instructions; if the
 calibration
value is correct, that will be a rate of 976.6 Hz.  The instructions, as coded a
bove, will
allow you to experiment to find the correct oscillator calibration value for the
 part without
having to erase it at all; if your code diesn't need addresses $1F8-$1FE, you ne
ed not erase
the part after measuring the value.

When the program is run (as written), it will use a calibration value of $80.  I
f this is too
fast, use $40 for the next attempt (movlw $3F xorlw $7F); otherwise use $C0 (mov
lw $3F xorlw
$FF).  It's possible to do a binary-search for the correct speed without having
to "unburn"
any bits, whereupon the desired speed may be left in $1FF.

Cool, huh?