LSI LSI22910, User Manual

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Interface Descriptions 1-5
1.3.4 Wide Ultra2 SCSI
The LSI22910 fully supports Wide Ultra2 SCSI. This interface is an
extension of the SCSI-3 family of standards that expands the bandwidth
of the SCSI bus to allow faster synchronous data transfers, up to
80 Mbytes/s. Wide Ultra2 SCSI provides a doubling of the data rate over
the Ultra2 SCSI interface, while it increases cable lengths and allows a
larger number of devices on the cable than Ultra2 SCSI interfaces.
Special SCSI cables are specified for operation with Wide Ultra and
Ultra2 SCSI devices. You must consider the total number of devices and
the length of your SCSI bus when setting up your system. See
Chapter 2,
“Installing the LSI22910,” for a more detailed explanation of SCSI bus
connections.
When you purchased the LSI22910 kit, the cable provided in the kit is
matched for a Fast/Ultra/Ultra2 SE or LVD operation. This cable also has
built-in LVD termination since most Ultra2 hard disk drives are not made
with on-board LVD termination.
Table 1.1 provides an overview of
standard SCSI cable specifications.
Table 1.1 Standard Cables
Maximum Bus Length, Meters
1
1. This parameter may be exceeded in point-to-point and engineered
applications.
STA Term SE LVD Maximum
Devices
Wide Ultra SCSI 1.5 Note
2
2. LVD was not defined in the original SCSI standards for this speed. If
all devices on the bus support LVD, then 12-meter operation is
possible at this speed. However, if any device on the bus is SE only,
then the entire bus switches to SE mode, and the distances in the
SE column apply.
8
Wide Ultra SCSI 3 Note
2
4
Wide Ultra2 SCSI Note
3
3. SE and high power differential are not defined at Ultra2 speeds.
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