A sub-genre of the speculative historical fiction genre called Steampunk. Clockpunk is characterized by modern technologies accomplished using clockwork mechanisms and generally excluding steam power, electricity, and the internal combustion engine. The chronological setting for Clockpunk fiction is pre-Industrial Revoluion, whereas steampunk is late 19th or early 20th century. A Clockpunk novel might include a world, Earth or another planet, which has been so dramatically revolutionized by DaVinci's mechanical inventions that its technology rivals our computers, phones, etc., while most other factors (some combination of social structure, ploitics, customs, clothing, etc.) would remail relatively true to the 15th century.
Gears and cogs but no steam...that's not Steampunk, its Clockpunk.