Abstract: A multi unit controller has a plurality of base units each of which includes a control unit connector, a base unit connector through which the base units juxtaposed to each other are connected to each other, and a plurality of control units connected to the base units respectively through the respective control unit connector, wherein the base units juxtaposed vertically.

Abstract: A failure is detected immediately and certainly, and continuation of processing in an unstable state is prevented. A first error detection code is generated from first information which is output as a result of execution of a predetermined program conducted by a first processor. A second error detection code is generated from second information which is output as a result of execution of the program conducted by a second processor which is configured so as to output the same computation result as that of the first processor. It is detected whether the first information is the same as the second information, and it is detected whether the first error detection code is the same as the second error detection code. Writing the first information or the second information into a main memory is controlled on the basis of a result of the detection.