Download the maniacbug core files for the 1284P here
and make a new boards.txt entry for the 644.
This has been posted in the forum before, you might be able to find it with a search also.
Update to 1.0.3 while you're at it.
Download the maniacbug core files for the 1284P here
and make a new boards.txt entry for the 644.
This has been posted in the forum before, you might be able to find it with a search also.
Update to 1.0.3 while you're at it.