INPUT/OUTPUT CONTROLLER FOR PROCESSOR SYSTEM

摘要

PROBLEM TO BE SOLVED: To efficiently transfer input/output data and to reduce the processing load of a central control unit in an input/output controller for processor system connected to the central control unit and main storage device through a system bus and transferring the input/output data of an input/output device to/from the main storage device. SOLUTION: This input/output controller 1-3 is provided with a channel controller 1-31 for controlling the transfer of the input/output data according to a channel command word(CCW) and a buffer 1-33 for CCW hold for storing and holding plural CCW and the buffer for CCW hold stores and holds the plural CCW together with addresses in the main storage device. Then, the channel controller reads the CCW out of the buffer for CCW hold when the starting instruction of a start input/output(I/O) instruction is received from a central control unit 1-1 and the CCW to be fetched exists in the buffer for CCW hold but reads the CCW out of the main storage device and stores/holds it in the buffer for CCW hold when such a CCW does not exist.