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SCSI Standards
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See tables at the end of this help file for definitions of several features of SCSI standards.
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Your choices are...
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SCSI-1
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SCSI-1, the original SCSI, was standardized by ANSI in 1986. It allows asynchronous data transfer rates of 1.5 MB/sec and synchronous transfer rates to a maximum of 5 MB/sec. It has an 8-bit SCSI port that uses Single-ended open-collector drivers. Uses a 50-pin connector. SCSI-1 is an obsolete standard after the development of SCSI-2.
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Wide SCSI
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This term is generally applied to Wide (16-bit) SCSI with a fast data transfer rate of up to 10 MBps.
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Fast SCSI
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Standard defined in SCSI-2. Increases the maximum data rate from 5 MBps for Narrow (8-bit) SCSI to 10 MBps.
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Wide Fast SCSI
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This term is generally applied to Wide (16-bit) SCSI with a fast data transfer rate of up to 20 MBps.
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Ultra SCSI
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This is also known as Fast-20. It doubles the FAST SCSI data rate to up to 20 MBps for the 8-bit bus
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Wide Ultra SCSI
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Wide Ultra SCSI defines a maximum transfer data rate up to 40 MBps for the Wide (16-bit) SCSI.
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SCSI-2
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SCSI-2 has significant improvements over SCSI-1 including faster data transfer rates, better connectors, wider bus path, better reliability via synchronous negotiation and parity checking. SCSI-2 has a data transfer rate from 5 MB/sec to 10 MB/sec. This speed change is called Fast SCSI-2. Also, SCSI-2 provides the option to double the bus from 8 bits to 16 bits. This change is known as Wide SCSI. By combining the Fast SCSI-2 with the Wide SCSI bus a maximum data rate of 20 MB/sec can be achieved.
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Ultra2 SCSI
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This is also known as Fast-40. It doubles the Ultra SCSI data rate to up to 40 MBps for the 8-bit bus.
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Wide Ultra2 SCSI
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Wide Ultra2 SCSI defines a maximum data rate of 80 MBps for the Wide (16-bit) SCSI.
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SCSI-3
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The SCSI-3 specification allows for faster transfer rate, more devices on a single chain (a maximum of 32), and also it incorporates serial connections in addition to the traditional parallel interconnect of SCSI-2. The serial interconnect of SCSI-3 incorporates three technologies: Serial Storage Architecture (SSA), Fibre Channel, and IEEE P1394. The serial transfer mode allows faster data rates, more devices per bus, simple connectors, and longer cables.
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Ultra3 SCSI (Ultra160)
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This is also known as Fast-80 or Ultra-160. It doubles the Ultra2 SCSI data rate to up to 160 MBps for the 16-bit bus.
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Ultra320 SCSI
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Defines a maximum data rate of 320 MBps for the Wide (16-bit) SCSI.
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Ultra640 SCSI
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Defines a maximum data rate of 640 MBps for the Wide (16-bit) SCSI.
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Fibre Channel
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A high-speed serial protocol for channels and networks that uses links of twisted-pair, coaxial cable or fiber optic cable. SCSI can use the Fibre Channel Arbitrary Loop (FC-AL) topology.
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Serial SCSI (FireWire®)
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A very fast bus standard that supports data transfer rates of up to 400 Mbps. FireWire is a registered trademark of Apple Computers, Inc. The standards are defined in IEEE 1394.
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Other
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Other unlisted, specialized, or proprietary SCSI standards.
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Search Logic:
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All products with ANY of the selected attributes will be returned as matches. Leaving all boxes unchecked will not limit the search criteria for this question; products with all attribute options will be returned as matches.
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Tables:
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Bus Width
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| Bus Width | | Width | Definition | | Narrow | Narrow SCSI is the conventional SCSI specified in the original SCSI. The bus width is 8 bits. | | Wide | Uses a data bus that is 16 bits wide. This doubling of the bus width respect to the Narrow SCSI comes at a higher cost, and it requires additional cabling and connectors. | | |
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SCSI Type
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| SCSI Type | | Type | Definition | | SCSI-1 | SCSI-1, the original SCSI, was standardized by ANSI in 1986. Allows asynchronous data transfer rates of 1.5 MB/sec and synchronous transfer rates to a maximum of 5 MB/sec. It has an 8-bit SCSI port that uses Single-ended open-collector drivers. Uses a 50-pin connector. SCSI-1 is an obsolete standard after the development of SCSI-2. | | SCSI-2 | SCSI-2 has significant improvements over SCSI-1 including faster data transfer rates, better connectors, wider bus path, better reliability via synchronous negotiation and parity checking. SCSI-2 has a data transfer rate from 5 MB/sec to 10 Mb/sec. This speed change is called Fast SCSI-2. Also, SCSI-2 provides the option to double the bus from 8 bits to 16 bits. This change is known as Wide SCSI. By combining the Fast SCSI-2 with the Wide SCSI bus a maximum data rate of 20 MB/sec can be achieved. | | SCSI-3 | The SCSI-3 specification allows for faster transfer rate, more devices on a single chain (a maximum of 32), and also it incorporates serial connections in addition to the traditional parallel interconnect of SCSI-2. The serial interconnect of SCSI-3 incorporates three technologies: Serial Storage Architecture (SSA), Fibre Channel, and IEEE P1394. The serial transfer mode allows faster data rates, more devices per bus, simple connectors, and longer cables. | | |
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Bus Speed
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| Bus Speed | | Speed | Definition | | Regular | This is the default speed of the original specifications of SCSI-1. The regular bus speed is 5 MHz. | | Fast | Fast SCSI increases the bus speed to 10 MHz. This doubling of the bus speed was defined in SCSI-2. | | Ultra | Also known as Fast-20, it is specified in SCSI-3. The bus speed of Ultra SCSI is 20 MHz. Ultra SCSI buses have a maximum transfer rate of 20 MB/sec for Narrow SCSI, and 40 MB/sec for Wide SCSI. | | |
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SCSI Standards
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| SCSI Standards | | | | | Maximum Bus Lengths (meters) | Max Devices Supported | | Protocol | Max Speed (MBps) | Bus Width (bits) | Single-ended | LVD | HVD | | | SCCI-1 | 5 | 8 | 6 | -- | -- | 8 | | Fast SCSI | 10 | 8 | 3 | -- | 25 | 8 | | Fast Wide SCSI | 20 | 16 | 3 | -- | 25 | 16 | | Ultra SCSI | 20 | 8 | 1.5 | -- | 25 | 8 | | Wide Ultra SCSI | 40 | 16 | 3 | -- | -- | 8 | | Ultra2 SCSI | 40 | 8 | -- | 12 | 25 | 8 | | Wide Ultra2 SCSI | 80 | 16 | -- | 12 | 25 | 16 | | Ultra3 SCSI (Ultra 160) | 160 | 16 | -- | 12 | -- | 16 | | Ultra 320 | 320 | 16 | -- | 12 | -- | 16 | | |
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Switch Configuration:
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Normally the configuration of a switch is specified, as b x c, where b is the number of independent SCSI host buses that the switch connects to, and c is the number of SCSI channels.
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Your choices are...
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1 x 2
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One host to 2 channels.
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1 x 3
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One host to 3 channels.
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1 x 4
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One host to 4 channels.
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2 x 1
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Two hosts to 1 channel.
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2 x 2
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Two hosts to 2 channels.
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3 x 1
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Three hosts to 1 channel.
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3 x 2
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Three hosts to 2 channels.
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3 x 3
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Three hosts to 3 channels.
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4 x 1
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Four hosts to 1 channel.
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4 x 2
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Four hosts to 2 channels.
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4 x 3
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Four hosts to 3 channels.
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4 x 4
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Four hosts to 4 channels.
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5 x 4
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Five hosts to 4 channels.
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5 x 5
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Five hosts to 5 channels.
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6 x 4
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Six hosts to 4 channels.
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Other
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Other unlisted, specialized, or proprietary configuration.
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Search Logic:
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All products with ANY of the selected attributes will be returned as matches. Leaving all boxes unchecked will not limit the search criteria for this question; products with all attribute options will be returned as matches.
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Built to Order?
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For nonstandard configurations, some companies will build switches order.
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Search Logic:
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"Required" and "Must Not Have" criteria limit returned
matches as specified. Products with optional attributes
will be returned for either choice.
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Communication Mode:
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Generally SCSI data can be transmitted synchronously or asynchronously. Asynchronous transfer is faster on short cables, while synchronous is faster on long cables.
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Your choices are...
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Synchronous Transfer
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A method of transferring data that does not require that the bus wait for a REQ-ACK handshake in order to deliver the next byte of data. The target is allowed to send certain number of REQ pulses without waiting for return ACK pulses. The number of REQ pulses that can be sent without waiting for an ACK is called the "offset." This method results in a better utilization of the bus bandwidth and produces a higher data rate than with asynchronous transfer.
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Asynchronous Transfer
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A method of transferring data where the bus must wait for a REQ-ACK handshake in order to deliver the next byte of data.
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Synchronous / Asynchronous Transfer
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The device can automatically detect the type of transfer mode that should be used between the initiator and the target.
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Search Logic:
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All products with ANY of the selected attributes will be returned as matches. Leaving all boxes unchecked will not limit the search criteria for this question; products with all attribute options will be returned as matches.
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Data Transfer Rate:
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The maximum data transfer rate (MB/sec) of the SCSI device.
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Search Logic:
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All matching products will have a value greater than or equal to the specified value.
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Product Form Factor
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The size, shape, and functional type of the SCSI product.
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Your choices are...
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Stand-alone Unit
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An independent unit connected to a system.
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Board-level Unit
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A computer board that is to be inserted in a carrier.
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ASIC
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Application Specific Integrated Circuit (ASIC) is a chip designed for a particular application. ASICs are manufactured by connecting existing circuits in new ways.
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Rack Mount
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A unit that can be mounted in a rack together with other units.
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Other
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Other unlisted, specialized, or proprietary configurations.
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Search Logic:
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All products with ANY of the selected attributes will be returned as matches. Leaving all boxes unchecked will not limit the search criteria for this question; products with all attribute options will be returned as matches.
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Control:
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Methods and devices used to control and manage the SCSI switch.
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Your choices are...
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RS232 Serial Port
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RS232 interface that allows remote interaction and control of the SCSI switch.
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Panel Control (LCD, or other)
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Front panel, normally menu-driven, used to control the SCSI switch.
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LAN Support
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Allows communication and control of the SCSI switch via TCP/IP.
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Manual Control
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An operator-driven selector (mechanical switch or push-button) to control the SCSI switch.
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Other
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Other unlisted, specialized, or proprietary configuration.
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Search Logic:
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All products with ANY of the selected attributes will be returned as matches. Leaving all boxes unchecked will not limit the search criteria for this question; products with all attribute options will be returned as matches.
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Redundant Power Supplies?
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More than one power supply for security.
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Search Logic:
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"Required" and "Must Not Have" criteria limit returned
matches as specified. Products with optional attributes
will be returned for either choice.
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Extends SCSI Distance?
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The device has the capability of extending the SCSI bus beyond the standard (5 meters for single ended signaling and 25 meters for differential signaling).
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Search Logic:
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"Required" and "Must Not Have" criteria limit returned
matches as specified. Products with optional attributes
will be returned for either choice.
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CE / FCC Certified?
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The unit conforms with the American requirements of the Federal Communication Commission (FCC) and with the European CE Marking (Conformite Europeene or European Conformity) system, which is helpful for exports to the countries of the European Economic Area (EEA).
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Search Logic:
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"Required" and "Must Not Have" criteria limit returned
matches as specified. Products with optional attributes
will be returned for either choice.
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