HP Array Controller HSG V8.7 Software - Manual (Page 26)

Introducing the UltraSCSI RAID Enclosure
1–4 UltraSCSI RAID Enclosure
An UltraSCSI Bus Overview
UltraSCSI was developed by Digital Equipment Corporation (now
Compaq Computer Corporation) and subsequently standardized by
the ANSI (American National Standards Institute) SCSI (small
computer system interface) committee as standard X3T10.
UltraSCSI is a technology that incorporates several improvements
over a Fast 10 SCSI bus.
UltraSCSI increases the maximum transfer rate on a wide (16-bit)
SCSI bus from 10 megabits per second (Mb/s) to 20 Mb/s. This
change increases the maximum bus bandwidth from 20 megabytes
per second (MB/s) to 40 MB/s for a wide (16-bit) SCSI bus.
UltraSCSI incorporates smaller very high density cable
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 StorageWorks UltraSCSI implements the bus segment concept.
An UltraSCSI bus segment is 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 are either single-ended or
differential, depending on the type of terminators used in that
segment. In other words, an UltraSCSI bus segment corresponds to
what Fast SCSI referred to as an entire SCSI bus. As in Fast SCSI, a
bus segment only supports devices of the same type as its terminators.
Do not, for example, attempt to use a differential SCSI bus device on
a single-ended SCSI bus segment.
Note
The Compaq UltraSCSI RAID enclosure only supports
single-ended UltraSCSI buses.