My laptop has an i5-4200M@2.5GHz and rest of the specs are same.
I tried running Black Flags on it, with everything low, frame rates are on an average of 25(@720p) and drops to 15 to 16 during naval warfare scenes where there is more particle rendering. I haven't tried with the latest drivers, but as far as I can say, 820m won't provide a minimum satisfactory playable framerate.