Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Interprocessor Communication Feature for Shared I/O Control Units

IP.com Disclosure Number: IPCOM000049141D
Original Publication Date: 1982-May-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Mitchell, MJ: AUTHOR

Abstract

Direct-Access Storage (DAS) control units are an example of today's "multi-tail" I/O boxes that provide for sharing by multiple processors (CPUs), as shown in Fig. 1. In many cases, DAS devices, disk files, attached to the DAS control unit, are also shared among the CPUs. A shared data base application would be an example. In these cases, high speed interprocessor communication (IPC) might be required in order to manage contention/locking of shared data. Current Channel to Channel Adapters (CCAs) can be used to control this authority by "passing the buck" from CPU to CPU in a sequential manner. As the number of required CPU links increases, the number of required CCAs becomes greater and more costly.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 46% of the total text.

Page 1 of 3

Interprocessor Communication Feature for Shared I/O Control Units

Direct-Access Storage (DAS) control units are an example of today's "multi- tail" I/O boxes that provide for sharing by multiple processors (CPUs), as shown in Fig. 1. In many cases, DAS devices, disk files, attached to the DAS control unit, are also shared among the CPUs. A shared data base application would be an example. In these cases, high speed interprocessor communication (IPC) might be required in order to manage contention/locking of shared data. Current Channel to Channel Adapters (CCAs) can be used to control this authority by "passing the buck" from CPU to CPU in a sequential manner. As the number of required CPU links increases, the number of required CCAs becomes greater and more costly.

A single control unit box, the Synchronizing Channel to Channel Adapter (SCCA) was developed to fulfill this type of requirement, as shown in Fig. 2 (see U.S. Patent 4,155,117). The subject of this article is an SCCA-like feature that could be implemented within a shared control unit, which would provide the desired IPC function. The DAS control unit will continue to be used as the example. Therefore, it is an object hereof to provide IPC functions in the DAS control unit at minimum additional product cost. It is a further objective that the SCCA connection criteria, the device address, will be used to connect two channel interfaces at the optimum time. It is a further objective that the SCCA connection conventions will be used in order to minimize the impact on CPU- diskfile transactions. It is an additional object of this arrangement that SCCA functions are mapped to existing file command sequences, such that the same access method could be used for IPC as for CPU-file. The error recovery procedures would necessarily be different. Lastly, it is an object to provide device planners an opportunity to minimize external dependencies for IPC from both a hardware and software standpoint.

From a design/product cost basis, an examination of a typical current DAS control unit design indicates much internal commonality with the SCCA implementation. They both have IBM System/370 Channel Interface control, a high speed data transfer capability, and a microprocessor for control functions. What would be added to the DAS control units is an SCCA-like cross-point switch to interconnect the channel interfaces for data transfer.

Up to 256 logical links, minus those assigned to DAS devices, will be allocatable among the attaching channels. These available CPU-CPU links are assignable by convention among the programs/users on the attached CPUs. The control unit action is to connect, at the proper time, two channels that use the same device address. These addresses must be recognized by the DAS control unit as requiring IPC communications, and so they must be pre-assigned outside the range of addresses assigned to the DAS devices. The exact method of categorizing the address ranges is in...