Abstract: Apparatus for implementing input/output (I/O) operations in a computer system operating under the control of a UNIX* operating system includes a dedicated communications processor in addition to the main or host processor. These two processors communicate via a shared memory which may be independently accessed by each processor. The functions performed by the terminal I/O driver and the line discipline modules are divided between the host and communications processors. The communications processor performs all canonical processing of the data received from the terminal I/O devices. It also maintains a data structure that indicates the instantaneous status of each terminal I/O device. Using this data structure, the communications processor is able to operate in a substantially interrupt-free environment, polling only those I/O devices that are indicated, in the status data structure, as needing service. A message facility in the shared memory controls communication between the processors.

Abstract: A common peripheral device interface module is disclosed for use with Unix (Unix is a trademark of AT&T) operating system which is flexible enough to support many types of disk or tape device drivers. A common disk module (CDM) is included. The CDM contains high level disk operation commands which may be used for common reference to each disk driver on the system. Routines within the CDM are accessed by the Unix system call interface through a series of operating system entry points. Additional routines are included with the pre-existing Unix operating system Disk I/O Subsystem to improve interfacing between this subsystem and the CDM. A common tape module (CTM) is used to perform high level tape operation routines. The Unix system call interface communicates with the CTM through a group of operating system entry points. Because of the large number of possible root disk device drives, the root disk device driver can be dynamically selected for the Unix operating system.