Control Unit Modified Channel Priority
Original Publication Date: 1979-Sep-01
Included in the Prior Art Database: 2005-Feb-20
Referring to Fig. 1, in a data processing system multiple channels 1, 2,..., indicated collectively at 3, may share input/output microprocessor (IOP) 4 and associated microprogram controls 4.1 for communicating with central processing/main storage complex 5. Each channel may communicate "externally" with multiple I/O control units (CU), and each control unit may connect multiple I/O devices (D) with the respective channel. In such systems the IOP may be driven by access (interruption) requests from the channels and attend to such requests in a fixed order of priority pre-assigned to the channels. However, this may expose time-dependent operations in low priority channels to possible overruns, which could be avoided at little expense by means of a simple adaptive priority scheme presented below.