The present article addresses the claim that the speed of information processing qualifies as a processing resource. This claim contends that age-related changes in processing speed pertain to all cognitive processes to the same proportional degree. That is, processing speed is compared to the clock speed of a microcomputer: as young children's clock speed increases, the speed of processing in all cognitive processes increases until the adult level is reached. Re-analyses of recent behavioral and psychophysiological data provide evidence against the notion that development is characterized by an increase in children's global clock speed, and refute the claim that processing speed operates as a mental resource on which all cognitive processes depend to the same extent. Rather, the results emphasize the role of inhibitory control in cognitive development, and we consider the relevance of inhibitory development to the issue of age-related changes in processing capacity.