Verification anyone...?
And they all verified? I haven't looked at the programming spec in a long time but I'll throw this out there. Parallel programming like this is frowned on. Fanout can be a problem from the programmer, but more importantly because of the acknowledge response from the IC during verify.
In general terms, when you program information is going back and forth between the programmer and the PIC (RB7 specifically during verify IIRC). How do you know which IC is verifying when you have them paralled like this? I'd say, you don't. I think some very "funky" (or another "f" word) things can happen under this scenario.
You may have got lucky by stacking a few devices, but if you are programming more than a couple, for anything more than your own use (I wouldn't want to know that something I bought had been programmed this way) I'd rethink this. Commercial gang programmers are readily available for doing this. These don't simply parallel all the pins; they usually have some dedicated circuitry so that each processor is programmed on it's own.
Head over to Microchip and search on ICSP; look at the process that takes place during a program cycle.
EDIT: I did the leg work for you (wasn't hard, went to the page of the device and looked for programming spec). Anyway, look at this: http://ww1.microchip.com/downloads/e...Doc/41204H.pdf
When programming RB7 is flipping back and forth between input/output. Play that out across 2 devices...5...10?
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