Compaq manual DS-DWZZH-05 Address Configurations

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conventional manner; the highest SCSI ID asserted during the arbitration cycle obtains use of the SCSI bus.

_______________________ Note _______________________

Host port SCSI ID assignments are not linked to the physical port when fair arbitration is disabled.

The DS-DWZZH-05 retains SCSI ID 7 regardless of whether fair aarbitrarion is enabled or not.

2.4 DS-DWZZH-05 Address Configurations

The DS-DWZZH-05 has two addressing modes; wide addressing mode and narrow addressing mode. With either addressing mode, if fair arbitration is enabled, each hub port is assigned a specific SCSI ID. This allows the fair arbitration logic in the hub to identify the SCSI ID of the device participating in the arbitration phase of the fair arbitration cycle.

_____________________ Caution _____________________

If fair arbitration is enabled, The SCSI ID of the host adapter must match the SCSI ID assigned to the hub port. Mismatching or duplicating SCSI IDs will cause the hub to hang.

SCSI ID 7 is reserved for the DS-DWZZH-05 whether fair arbitration is enabled or not.

Jumper W1, accessible from the rear of the DS-DWZZH-05 (see Figure 2–2) determines which addressing mode is used. The jumper is installed to select narrow addressing mode and is presently the only addressing mode supported with Compaq's DIGITAL UNIX operating system. If fair arbitration is enabled, the SCSI IDs for the host adapters are 0, 1, 2, and 3 (see the port numbers not in parentheses in Figure 2–1). The controller ports are assigned SCSI IDs 4 through 6, and the hub uses SCSI ID 7.

If jumper W1 is removed, the host adapter ports assume SCSI IDs 12, 13, 14, and 15. The controllers are assigned SCSI IDs 0 through 6. The DS-DWZZH-05 retains the SCSI ID of 7.

2–4Using the DS-DWZZH-05 UltraSCSI Hub in a Cluster Configuration

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Contents December Operating System and Version Compaqs Digital Unix VersionCompaq Computer Corporation Houston, Texas Page Contents Tables Audience OrganizationPage DS-DWZZH-05 UltraSCSI Hub General OverviewDS-DWZZH Overview DS-DWZZH-05 UltraSCSI Hub Description DS-DWZZH-05 Configuration GuidelinesDS-DWZZH UltraSCSI Hub Maximum Configurations Disk Drivesa Personality Moduleb cDS-DWZZH-05 Fair Arbitration Disk Drives a Personality Module b cDS-DWZZH-05 Address Configurations DS-DWZZH-05 Front View Scsi Bus Termination Power DS-DWZZH-05 IndicatorsConfiguring a Cluster with a DS-DWZZH-05 Installing the DS-DWZZH-05 UltraSCSI Hub Cabling an HSZ50 to a DS-DWZZH-05 UltraSCSI Hub DS-DWZZH-05 Callout Number Description BN21K or BN21L HD68 cable bKZPBA-CB BN38C HD68 to Vhdci cablea