Control system for interruption long data transfers between a disk unit or disk coche and main memory to execute input/output instructions

Claim 1

A control system for a disk cache memory disposed between a main memory unit and a disk unit, including a disk cache controller comprising: an upper interface control for receiving an input/output instruction from a central processing unit (CPU), for judging, in response to said input/output instruction, whether object data is found in said disk cache memory, and for controlling data transfer, based on a result of the judgement, of said object data from said disk cache memory if said object data is found in said disk cache memory, or from said disk unit if said object data is not found in said disk cache memory to said main memory unit; and a lower interface control for controlling data transfer from said disk unit to said disk cache memory; wherein said upper interface control includes first means for accessing said lower interface control and recognizing whether said lower interface control has performed a data transfer from said disk unit to said disk cache memory, and second means for accessing said first means and providing, when the recognition performed by said first means is positive, a command to said lower interface control interrupting the data transfer being performed thereby; wherein the data transfer performed by said upper interface control upon reception of said input/output instruction from said CPU is executed after said lower interface control receives a command from said second means interrupting the data transfer from said disk unit to said disk cache memory being performed by the lower interface control.