the 644 version predates my involvement and hasn't been tested
Quotethe 644 version predates my involvement and hasn't been testedWell, now it's been tested.It doesn't work.It has the wrong signature for an ATmega644p (it makes it look like an ATmega644.)You can tell boards.txt that you have a 644 and upload will work, but then the pins_arduino.c doesn't get correct values.(and why does it have an incorrect signature byte? Because avr-libc is actually wrong in the version that ships with Arduino. It's not even an optiboot bug. Sigh. https://savannah.nongnu.org/bugs/?26188It also has an incorrect efuse value in the Makefile (should be 0xFD, with the "unused" bits set to 1, but the makefile has 0x05)http://code.google.com/p/optiboot/issues/detail?id=61
The source at http://code.google.com/p/optiboot/ has been fixed, and I've added a .hex file for 644p to the download area.It's still tagged as v4.5, since this didn't change any object code of previously supported platforms. And like the 1284p support, the 644p is not an official Arduino team platform, so this won't be committed to the Arduino repository until it's time for some sort of big "upgrade."