Digital Equipment Corporation

Mike Hare

Stephen J Sicola

Bruce A Sardeson

Frank M Nemeth

Brian Schow

In a SCSI subsystem having mixed wide and narrow SCSI devices installed, a method and apparatus is provided for detecting a narrow SCSI device illegally installed at a slot assigned to a wide SCSI device. To detect the narrow SCSI device installed at an illegal location, high ID and low ID SCSI bus address pairs are set as test pairs for the SCSI subsystem. The low ID is the alias of the high ID if a narrow SCSI device is installed at the high ID slot. To detect a conflict with a controller ID, a non-responsive ID bus address corresponding to a slot known to be unused is called. A response to this call indicates a narrow SCSI device is installed at the high ID of the test pair and the narrow SCSI device at the high ID has configured to an alias bus address matching the controller ID. To detect a present conflict between SCSI devices, the low ID bus address in the test pair is called. A conflict in responses indicates a SCSI device is installed at the low ID and a narrow SCSI device is installed at the high ID of the test pair. To detect a future conflict between a narrow SCSI device at a high ID and a SCSI device installed in the future at an unused low ID, both the low ID and the high ID are called. No response to the high ID call in combination with a response to the low ID call indicates a narrow SCSI device is installed at the high ID and the narrow SCSI device would conflict in the future with a SCSI device subsequently installed at the unused low ID.

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Colorado Springs, CO, United States of America

Mike Hare