The smallest ever ATmega644/1284-based board will soon be launching via the Crowd Supply website offering a perfect development board and micro-controller for your smaller projects. Very soon the ATmega644/1284-based board will be available to purchase although no pricing or availability have been revealed as yet for the 644 Narrow and 1284 Narrow.
“644 Narrow and 1284 Narrow are the simplest and perfect upgrade option for all your small footprint Arduino projects. The Narrow board gives you 2 to 8 times more flash and RAM resources as compared to a Uno/Nano, plus total compatibility”.
– A large amount of effective Flash and RAM. Effective because the code generated on 8-bit MCUs is much smaller than on 32-bit MCUs. Hence you can load a bigger program on these 64k/128k MCU than on a 256k 32 bits MCU! ATmega644/1284 also have EEPROM that adds to the total storage capabilities.
– A small footprint. Narrow boards are approximately 1/5 the of the surface of an Arduino Mega 2560 board, and half its current consumption.
– Perfect Arduino compatibility. Ten more digital I/Os and one more UART port than an Arduino Nano.
– Best choice for your 5 volts projects.
Source : Crowd Supply