Scsi Interface Cable Requirements; Mating Connectors - Seagate ST3146855LC - Cheetah 146.8 GB Hard Drive Product Manual

Table 16 shows the interface transfer rates supported by the various drive models defined in this manual.
Table 16: Interface transfer rates supported
Interface type/
drive models
SE ST3300655LW/LC
ST3146855LW/LC
ST373455LW/LC
LVD ST3300655LW/LC
ST3146855LW/LC
ST373455LW/LC
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 Ultra320 SCSI parallel interface devices are discussed in detail
in Section 6 of ANSI Standard T10/1365D Rev. 3. The cable characteristics that must be considered when
interconnecting the drives described in this manual in a Ultra320 SCSI parallel, daisy-chain interconnected
system are:
• characteristic impedance (see T10/1365D Sections 6.3.3 and 6.3.4)
• propagation delay (see T10/1365D Sections 6.3.6 and 6.3.7)
• stub length (see T10/1365D Section 6.9)
• device spacing (see T10/1365D Section 6.9)
To minimize discontinuances and signal reflections, cables of different impedances should not be used in 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 and Fast-160 operation, twisted pair cables are
required.
LC Models
The 80-pin connector option provided on LC models is intended for use on drives that plug directly into back-
plane connector in the host equipment. In such installations, all backplane wiring segments are subject to the
electromagnetic concepts presented in Standard T10/1365D, Rev. 3, Section 6. For LC model drives, installa-
tions with connectors on cables are not recommended.
9.6.4

Mating connectors

Part numbers for the different type connectors that mate with the various Cheetah 15K.5 SCSI I/O connectors
are given in the sections following.
Cheetah 15K.5 SCSI Product Manual, Rev. H
Maximum transfer rate
Asynchronous
Fast-5
yes yes
yes yes
Fast-20 Fast-40
Fast-10 (Ultra) (Ultra2)
yes yes no
yes yes yes
Fast-80 Fast-160
(Ultra160) (Ultra320)
no no
yes yes
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