Let me start off by saying this is the ATmega644-20PU (and NOT the 644P).
I’ve successfully used Arduino as ISP to burn bootloaders to '328 chips, and now I’m trying it with some 644s.
When I try it, I get the “YIKES! Invalid device signature!” error from AVRdude. As I didn’t have any 16MHz oscillators on hand, I was rigging another arduino’s crystal (through the chip socket) to the fresh 644.
I’m hoping the error is because of the long (4-6 inch) wires I’m using to connect the crystal, which is causing problems. Could that cause this problem? Is it likely? If so, I’ll just have to wait for my digikey shipment to get here to flash these things…
By the way, I also get the same error without any crystal, making me think more that it is an interference problem.