Digital Equipment StorageWorks UltraSCSI DS-BA370 Series, User Manual

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Introducing the Ultra SCSI RAID Enclosure
1–4 UltraSCSI RAID Enclosure
An UltraSCSI Bus Overview
Developed by the Digital Equipment Corporation and subsequently
standardized by the ANSI (American National Standards Institute) SCSI
committee as standard X3T10, UltraSCSI is a technology that incorporates
several improvements over a Fast SCSI 10 bus.
UltraSCSI increases the maximum transfer rate on a wide (16-bit) SCSI bus
from 10 MHz (mega Hertz) to 20 MHz. This results in an increase in
maximum bus bandwidth from 20 MB/sec (mega bytes per second) to
40 MB/sec.
UltraSCSI incorporates smaller very high density computer interconnect
(VHDCI) cables and connectors. The connector is up to half the size of the
Fast SCSI HD68 (high-density 68-pin) connector and the cables are thinner.
The higher speed of the single-ended UltraSCSI signals can cause
degradation of signal integrity over the same distances as single-ended Fast
SCSI signals. However, the UltraSCSI bus can run over much greater
distances than Fast SCSI in either single-ended or differential mode. To
attain these greater distances, UltraSCSI defines, and the StorageWorks
UltraSCSI implements the bus segment concept.
An UltraSCSI bus segment is as an unbroken electrical path consisting of
conductors (in cables or on backplanes) and connectors. Every UltraSCSI
bus segment must have two terminators, one at each end of the bus
segment. Bus segments can either be single-ended or differential, depending
on the type of terminators used in that segment. In other words, an
UltraSCSI bus segment corresponds to what in Fast SCSI was an entire
SCSI bus. As in Fast SCSI, a bus segment can only support devices of the
same type as its terminators. You cannot, for example.
Use a differential SCSI device on a single-ended bus segment.
______________________Note _____________________
The DIGITAL UltraSCSI RAID enclosure only supports the
single-ended UltraSCSI bus.
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