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Adaptec SCSI RAID 2010S/2015S Installation Guide
Narrow and Wide SCSI Devices
You can attach either narrow (8-bit) or wide (16-bit) SCSI devices to
your Adaptec ZCR controller. If you use narrow and wide devices
on the same wide cable, put one of the wide devices at the end of
the cable. This ensures that the 16-bit signals are correctly
terminated.
Wide devices allow data to be transferred at twice the rate of
narrow devices. The wide bus is backward compatible with narrow
devices, allowing both types of SCSI devices to be used with the
same controller. The narrow interface is still used with some SCSI
devices, such as tape and CD drives.
LVD and SE Devices
Attaching a single-ended (SE) SCSI device to a Low Voltage
Differential (LVD) bus causes the bus to slow down to Ultra SCSI
speed (20 MHz) for all devices.
Note: Adaptec ZCR controllers cannot be used with older SCSI
5-V differential (DE) devices.
SCSI Cables
Adaptec recommends using Ultra320 SCSI devices and good
quality LVD SCSI cables.
SCSI Device IDs
A narrow SCSI bus can support up to 7 SCSI devices and a
controller connected to a single 8-bit SCSI bus. A wide SCSI bus can
support up to 15 devices and the controller connected to its 16-bit
bus.
All SCSI devices, including the controller, must be assigned a
unique SCSI ID. SCSI IDs, which are typically set using jumpers or
switches on peripheral devices, can be assigned any number from 0
to 7 for 8-bit SCSI devices or 0 to 15 for wide SCSI devices. Some
computer systems and hard disk drive towers offer intelligent
backplanes (SAF-TE / SES) that automatically assign a fixed SCSI
ID to each slot in the backplane. When using these types of
backplanes it is not necessay to assign an ID to each SCSI device.
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