programming multiple parts on 1 board with 1 ISP connector

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OK, so I think this has been talked about before, and maybe even recently, but search didn't turn up anything.

If I have multiple AVR's on one board, how can I program them all with one ISP conector? Is there a standard trick? Or an Atmel ap note that I missed?

Seems to me that selecting using reset is a bad idea, since you want all the board held in reset, and any AVR in reset will go into programming mode, resulting in a muddle. My first guess at doing it correctly would be to wire up reset, mosi, and miso in parallel to all AVR's, and then route sck through a de-mux of some flavor. Routing sck through a jumper such that the device being programmed is being fed ssk and the others have a floating sck would also seem to be a bad idea, since reset disables internal pull-ups. So... a weak pull-up on everybody's sck? And then you have the issue of sck needing to go everywhere during normal spi operation.

I need a clue.

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OK, so I just re-read AVR042 -- seems I missed this paragraph on the last pass -- it says to send sck to one processor at a time.

So... what's the simplest, cheapest trick to do that? Anybody got a good one they like?