1.3b is definitely using a ATmega1284b as Controller.
Taken from the Wiki:
Taken from the Wiki:
Version 1.3b - Updated April 4, 2012 With this revision the Sanguinololu is updated with SMT components, leaving more room on the board for more connectors and singleside mount. The board is fully compatible with the previous version and the pin assignments remain the same. The hardware changes: The Atmel ATMEGA644P is changed to Atmel ATMEGA1284p SMT version, leaving much more room on the board. MOSFET changed to SMT versions capable of 76A drain current! The Molex HDD connector is back on the board. 3 pin terminal for both +5V, +12V and GND connections. Connectors for both 3pin Opto Endstops or 4pin Mechanical Endstops. 5V or 12V.