Note(s):
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Pictures may not
reflect actual items.
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Specifications may
change without notice, subject to manufacturers.
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SCSI Terminators vs Wrap Tool - IBM
Verification
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Type of SCSI (info source: https://whitefiles.org)
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SCSI-1
This, the original form of SCSI, uses an 8-bit connection, as
defined by the American National Standards Institute
(ANSI) standard X3T9.2. It appears on the early Mac OS machines,
conveying data at up to 5 MB/s. Standard single-ended
(unbalanced) wiring is used, permitting cables up to six meters in
length, although some specialist hardware has differential
(balanced) wiring, extending this limit to 25 meters. Most Mac
OS computers have a DB25 or HDI30 socket, whilst SCSI devices have a
matching plug or two C50 sockets. Up to eight devices, including the
computer, can be connected at once. Connections are made via one of
the following types of connector.
25-way D (DB25)
30-way rectangular (HDI30)
50 way C (Amphenol) (C50)
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Fast Wide SCSI-2
This version conveys 16-bit data at up to 20 MB/s via a 68-way
high-density D connector (HD68). All devices incorporate active
termination, eliminating the need for an external terminator (see
below). A total cable length of up to 12 meters is permitted. Up to
15 devices can be connected, whilst 32-bit data can be accommodated
at 40 MB/s by using paired HD68 connectors or a special 104-way
connector.
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Ultra Narrow SCSI-3
This basic form of Ultra SCSI uses a special technique to double the
original speed of narrow SCSI to 20 MB/s whilst retaining full
compatibility with SCSI-1 and the narrow form of SCSI-2.
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Ultra Wide SCSI-3
This 16-bit form of Ultra SCSI works at up to 40 MB/s, conveying
data via a 68-way high-density D connector (HD68). All devices
incorporate active termination, eliminating the need for an external
terminator (see below). However, an external active terminator,
known as an Ultra Wide SCSI-3 terminator, can also be used if
required. Up to 15 devices can be connected, whilst 32-bit data is
accommodated using paired HD68 connectors or a special 104-way
connector. A typical PCI card, providing two SCSI ports, will often
be found to have a pair of micro-C 68-way connectors.
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Ultra 2 Narrow SCSI
This interface uses low-voltage differential (LVD) technology, but
is compatible with older forms of SCSI. It uses lower voltage
signals, enabling it to run at up to 40 MB/s. The Ultra 2 SCSI
terminator, although similar in appearance to an Ultra-Wide SCSI-3
terminator, is designed specifically for Ultra 2 SCSI
devices. HD68 connectors are preferred for this kind of interface.
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Ultra 2 Wide SCSI
This also uses LVD technology (see above) and is compatible with
Ultra Wide SCSI-2, but runs at speeds of up to 80 MB/s. The Ultra 2
Wide SCSI terminator, although similar in appearance to an Ultra
Wide SCSI-3 terminator, is designed specifically for Ultra 2 Wide
SCSI devices. HD68 connectors are preferred for this kind of
interface.
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Ultra 3 Narrow SCSI
This development of SCSI, also known as Ultra 80 or Fast-80, works
at up to 80 MB/s, with HD68 connectors preferred.
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Ultra 3 Wide SCSI
This later version of SCSI, also known as Ultra 160, works at up to
160 MB/s, with VHD68 or HD68 connectors preferred.
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Ultra 320 SCSI
An emerging SCSI format, providing speeds of up to 320 MB/s.
- Type
of SCSI
(info source: computer.howstuffworks.com/scsi.htm)
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SCSI-1:
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Asynchronous SCSI
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Number of Drive: 8 Drive
- Bus
Width: 8bit
- Bus
Speed: 5MHz
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Megabits Per Second: 4MBPs
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Synchronous SCSI
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Number of Drive: 8 Drive
- Bus
Width: 8bit
- Bus
Speed: 5MHz
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Megabits Per Second: 5MBPs
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SCSI-2:
- Wide
SCSI
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Number of Drive: 16 Drive
- Bus
Width: 16bit
- Bus
Speed: 5MHz
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Megabits Per Second: 10MBPs
- Fast
SCSI
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Number of Drive: 8 Drive
- Bus
Width: 8bit
- Bus
Speed: 10MHz
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Megabits Per Second: 10MBPs
- Fast
Wide SCSI
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Number of Drive: 16 Drive
- Bus
Width: 16bit
- Bus
Speed: 10MHz
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Megabits Per Second: 20MBPs
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SCSI-3:
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Ultra SCSI (SCSI Parallel Interface SPI)
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Number of Drive: 8 Drive
- Bus
Width: 8bit
- Bus
Speed: 20MHz
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Megabits Per Second: 20MBPs
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Ultra Wide SCSI (SCSI Parallel Interface SPI)
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Number of Drive: 8 Drive
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Bus Width: 16bit
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Bus Speed: 20MHz
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Megabits Per Second: 40MPBs
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Ultra 2 SCSI (SCSI Parallel Interface SPI-2)
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Number of Drive: 8 Drive
- Bus
Width: 8bit
- Bus
Speed: 40MHz
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Megabits Per Second: 40MPBs
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Ultra 2 Wide SCSI (SCSI Parallel Interface SPI-2)
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Number of Drive: 16 Drive
- Bus
Width: 16bit
- Bus
Speed: 40MHz
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Megabits Per Second: 80MBPs
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Ultra 3 SCSI (SCSI Parallel Interface SPI-3)
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Number of Drive: 15 Drive
- Bus
Width: 16bit
- Bus
Speed: 40MHz
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Megabits Per Second: 160MBPs
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Ultra 320 SCSI (SCSI Parallel Interface SPI-4)
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Number of Drive: 16 Drive
- Bus
Width: 16bit
- Bus
Speed: 80MHz
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Megabits Per Second: 320MBPs
- SCSI
Terminator:
A Resistor Circuit added to the last device of the SCSI series to
terminate the SCSI Bus. If the SCSI Bus were left open, signal sent
down the bus could reflect back and interfere with communication
between devices and the controller.
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Passive Terminator:
Used for Standard Clock Speed System with a distance of less than
3FT.
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Active Terminator:
Used for Fast Clock Speed System with a distance of more than 3FT.
- SE
Terminator:
Single Ended, the controller generates the signal and pushes it out
to all devices over a single data line. The signal quickly to
degrade which limits the SE SCSI to a maximum distance about 10FT.
- LVD
Terminator:
Low Voltage Differential, the transceivers are smaller and built
into each device to make them more affordable and use less
electricity for system with a distance up to 40FT.
- HVD
Terminator:
High Voltage Differential, each device has a built in signal
transceiver using tandem approach signaling with a data high line
and a data low line. Often used for server with the distance up to
80FT.   
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