Input/Output Supervisor Dynamic Processor Signalling
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
A major consideration in any multiprogramming operating system is the design of the I/O Supervisor (IOS). Previously, IOS was designed to be capable of operating asynchronously with respect to user program requests, and even to many other portions of the operating system. This can allow IOS to control the devices and other I/O hardware with high utilizations. This article describes special IOS logic to coordinate operations with user program requests, as well as to minimize both overhead and delay. In prior tightly coupled multiprocessor systems having most devices attached by multiple paths to both processors, IOS selected a path to a requested device. IOS does this by determining if any paths are available to the device on the processor IOS happens to be using at that time.