A microcomputer provided on a rectangular semiconductor board has memory interface circuits. The memory interface circuits are separately disposed in such positions as to extend along the peripheries of the semiconductor board on both sides from one corner as a reference position. In this case, limitations to size reduction imposed on the semiconductor board can be reduced compared with a semiconductor board having memory interface circuits only on one side. Respective partial circuits on each of the separated memory interface circuits have equal data units associated with data and data strobe signals. Thus, the microcomputer has simplified line design on a mother board and on a module board.