PURPOSE: To increase the speed of an operation through a computer system bus interface.

CONSTITUTION: This system consists of a process where plural sets of data are written in data registers of a second computer module and a specific command related to each set of data is started in the case of non-existence of exceptions of the set of data, a process where a retry command is issued in the case of the existence of a register full exception of any set of data, a process the state of the second computer module is read once for all sets of data to detect data or sets of data as causes of exceptions other than the register full exception in the case of the existence of theses exceptions, a process where a central processing unit is made execute a command related to sets of data as causes of individual exceptions other than the register fill exception, and a process where the operation to write data following data or a set of data as the cause of an exception in a data register of the second computer module is continued and a specific command related to this data is started in the case of non-existence of exceptions of this data.