A printhead uses large and small drop ejectors to achieve efficient gray scale printing. The bus arbitrator of the data includes a timer for counting down use permission time with respect to the channel having the high necessity of the real-time processing operation, and a register for the channel having the low necessity of the real-time processing operation. In another embodiment, the gas distribution plate has a first flowing channel passing through a first and a second surface of the gas distribution plate, a second flowing channel paralleling to the first surface and a third flowing channel disposed at the second surface and communicating with the second flowing channel. Additionally, a stiffening structure is formed to increase the overall rigidity of the thin substrate specifically and the package as a whole.