there are a few 644p bootloaders about that dont actuly work. And you need the correct one for the correct frequency your runing the chip at (16 or 20 mhz normaly) And since the IDE also sets the fuses, which selects if your using a resinator or a crystal you may also need to play with the boards.txt file to change the fuses.
These are known to work well. [reprap.org]
Ie download and use [github.com] as the boot loader
These are designed for a crystal.
You havent mentioned what board you actuly have...
These are known to work well. [reprap.org]
Ie download and use [github.com] as the boot loader
These are designed for a crystal.
You havent mentioned what board you actuly have...