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Multiple-I-O-bus-virtual-broadcast-of-programmed-I-O-instructions

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Details

Inventors: Presant, Stephen D.;
Assignee: Prime Computer, Inc. (Natick, MA)
Primary Examiner: Williams, Jr.; Archie E.
Assistant Examiner: Mohamed; Ayni
Attorney, Agent or Firm: Wolf, Greenfield & Sacks

A method of performing an input/output process containing a programmed input/output (PIO) instruction in a multiprocessor system including at least two processors each having an associated I/O bus with I/O devices connected thereto. The method has the steps of storing a unique address and a bus location for each I/O device in a device location table, determining the address of a referenced I/O device prior to performing the PIO instruction, reading the corresponding I/O bus location of the referenced I/O device from the device location table and executing the input/output process on the prescribed processor associated with the I/O bus to which the referenced I/O device is located. The method is used in conjunction with a task scheduler including a process control block for each scheduled process. When the PIO instruction references a device on the local I/O bus, the input/output process is executed normally. To execute the input/output process on a remote processor, a locked descriptor identifying the remote processor is placed in the process control block for that process. The input/output process is then scheduled for execution on the remote processor.

DETAILED DESCRIPTION According to the present invention, these and other objects and advantages are achieved in a method for performing an input/output process containing a programmed input/output instruction in a multiprocessor system including at least two processors, each having an associated I/O bus with one or more I/O devices connected thereto.
The method comprises the steps of storing a unique I/O device address and an I/O bus location for each I/O device in a device location table, determining the address of a referenced I/O device prior to performing the programmed input/output instruction, reading the corresponding I/O bus location of the referenced I/O device from the device location table, and executing the input/output process on the processor associated with the I/O bus to which the referenced I/O device is connected.
The multiprocessor system includes process scheduling means for scheduling and running processes according to their priorities.
The process scheduling means includes a process control block associated with each scheduled process.
The step of executing the input/output process includes the steps of executing the input/output process on the local processor when the referenced I/O device is connected to the local I/O bus and, when the referenced I/O device is connected to a prescribed remote I/O bus, placing a locked descriptor in the process control block of the input/output process, the locked descriptor indicating that the input/output process can be performed only on the remote processor associated with the prescribed remote I/O bus, saving the registers of the input/output process in its process control block, and scheduling the input/output process in accordance with its priority on the remote processor associated with the prescribed remote I/O bus.
The method of the present invention results in the software effectively providing a virtual broadcast of programmed input/output operations to all I/O devices connected to the system.
The term "virtual broadcast" is appropriate because the software appears to communicate with an I/O device located on any I/O bus when it executes a programmed input/output instruction

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