Scsi Interface Cable Requirements - Seagate ST336732LC Product Manual

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Table 15: Interface transfer rates supported
Maximum transfer rate
Interface type/
drive models Asynchronous
ST336752
SE LW yes
ST336752
LC
ST318452LW
ST318452
LC
ST336752
LVD LW yes
ST336752
LC
ST318452LW
ST318452
LC
SE ST336732LW yes
ST336732LC
ST318432LW
ST318432LC
LVD ST336732LW yes
ST336732LC
ST318432LW
ST318432LC
9.6.3

SCSI interface cable requirements

The characteristics of cables used to connect parallel interface drives are discussed in the ANSI standards ref-
erenced in this section.
9.6.3.1 Cable requirements
The characteristics of cables used to connect Ultra160 and Ultra320 SCSI parallel interface devices are dis-
cussed in detail in section 6 of the SPI-4 standard. The cable characteristics that must be considered when
interconnecting the drives described in this manual in a SCSI parallel, daisy-chain interconnected system are:
• characteristic impedance (see SPI-4 sections 6.3.3, 6.3.4, and 6.3.5)
• propagation delay (see SPI-4 sections 6.3.6 and 6.3.7)
• cumulative length (see SPI-4 sections 6.6 and 6.8)
• stub length (see SPI-4 sections 6.6 and 6.9)
• device spacing (see SPI-4 sections 6.6 and 6.9)
To minimize discontinuances and signal reflections, cables of different impedances should not be used on the
same bus. Implementations may require trade-offs in shielding effectiveness, cable length, number of loads
and spacing, transfer rates, and cost to achieve satisfactory system operation. If shielded and unshielded
cables are mixed within the same SCSI bus, the effect of impedance mismatch must be carefully considered.
Proper impedance matching is especially important in order to maintain adequate margin at Fast-20, Fast-40,
Fast-80, and Fast-160 SCSI transfer rates.
Note. For LVD operation, twisted pair cables are recommended. For LVD Fast-40 operation, twisted pair
cables are strongly recommended. For Fast-80 or Fast-160 operation, twisted pair cables are required.
All LC model drives:
The 80-pin connector option is intended for use on drives that plug directly into backplane connector in the host
equipment. In such installations, all backplane wiring segments are subject to the electromagnetic concepts
presented in section 6 of the SPI-4 standard. For LC model drives, installations with connectors on cables are
not recommended.
Cheetah X15 36LP Product Manual, Rev. D
Fast-20
Fast-5 Fast-10 (Ultra)
yes yes yes
yes yes yes
yes yes yes
yes yes yes
Fast-40 Fast-80
(Ultra2) (Ultra160)
no no
yes yes
no no
yes yes
Fast-160
(Ultra320)
no
no
no
yes