Browse Prior Art Database

SCSI Bus Passthrough Terminator

IP.com Disclosure Number: IPCOM000110106D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Frazier, GR: AUTHOR [+2]

Abstract

The SCSI bus is a multi-drop parallel bus used to interconnect peripheral devices, such as disk drives, to a host controller. In order for the bus to function, it must have a terminator on both ends of the bus. A typical configuration is shown in Fig. 1. This figure depices a single host controller (Adapter card) controlling several SCSI disk drives.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 55% of the total text.

SCSI Bus Passthrough Terminator

       The SCSI bus is a multi-drop parallel bus used to
interconnect peripheral devices, such as disk drives, to a host
controller.  In order for the bus to function, it must have a
terminator on both ends of the bus.  A typical configuration is shown
in Fig. 1.  This figure depices a single host controller (Adapter
card) controlling several SCSI disk drives.

      The SCSI bus may also be used by multiple hosts to share disks,
as shown in Fig. 2.  Each host controller (Adapter card) allows its
host system to use any of the disks.  In this figure, however, if one
of the host systems needs to be removed for service, the SCSI bus
must be broken at the Connector.  This results in removal of the
terminator and renders the entire SCSI bus inoperable until a
terminator is reconnected.  This may not be acceptable in systems
which have two hosts on the SCSI bus in order to ensure continuous
availability of the disk drives.  This problem may be solved,
however, by the Passthrough Terminator disclosed here.  The use of
the Passthrough Terminator to solve this problem is shown in Fig. 3.

      In Fig. 3, note that either Host may be removed at the
Connector, and the SCSI bus will still have terminators at both ends.
Since the bus still has a terminator at each end even after one host
is removed, the other host system can continue to use the disk
drives.  Since the terminator never needs to be removed from the SCSI
bus even as o...