Quote Originally Posted by peterdeco1 View Post
Simply stack one PIC on top of each other so that all the pins are in parallel and all will program. If you stack say 6 and the 4th one up isn't connected then the chain is broken and 4,5 and 6 won't be programmed.
I second this; never had a problem. Been cascading chips like this since the good old 27XX EPROM days.