ATTO Technology UL25 Cabling for the Atto ExpressPCI UL2S & UL2D Scsi Adapters, Cable Types

CHAPTER 3: CABLING AND TERMINATION

ATTO ExpressPCI Ultra2 SCSI host adapters are designed to operate with either low voltage differential or single-ended devices. When connected to single-ended devices, ATTO ExpressPCI Ultra2 negotiates to Ultra/WIDE transfer rates of 40 Mbytes/sec. per channel. When connected to Ultra2/WIDE devices, ATTO ExpressPCI Ultra2 negotiates to Ultra2/WIDE transfer rates of 80 Mbytes/sec. per channel.

To determine your ATTO ExpressPCI Ultra2 SCSI host adapter model, check the label located on the serial number end of the product box. The model you have will be printed on the barcode label. After determining whether you are using a single channel or dual channel model, the next step in the cabling and termination process is to identify whether SCSI devices will be installed internally or externally. This determines which cables are used and how to connect your SCSI device terminators.

Cabling for the ATTO ExpressPCI UL2S & UL2D SCSI Adapters

The ATTO ExpressPCI UL2S has one industry standard 68-pin “P” (16-bit) VHDCI (Very High Density Cabled Interconnect) cable connector for external device connections and one 68-pin “P” (16-bit) cable connector for internal device connections. The ATTO ExpressPCI UL2D has two industry standard 68-pin “P” (16- bit) VHDCI cable connectors.

By definition, the Ultra2 SCSI specification limits the total bus cable length to 12 meters or approximately 38 feet (this is a combined figure of both internal and external cable lengths). Try to keep cable lengths as short as possible to ensure higher signal quality and performance.

If using a combination of Wide 16-bit devices and Narrow 8-bit devices on the same connector, Wide devices must be connected first (closest to the connector), followed by the Narrow devices. Please refer to the documentation for your SCSI devices to determine if device is Wide or Narrow, and if it is an UltraSCSI or Ultra2 SCSI device.

Cable Types

With all varieties of SCSI, be sure to use high quality SCSI-3 rated, well-insulated SCSI cables to ensure error free communications. The following illustrations depict the types of internal and external cable connectors you may come across.

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