Using the Integrated SCSI Controllers 7-1

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This chapter pr ovi des in structions for instal ling drivers for the following SCSI
controllers:
Integrated Adaptec 7890 Ultra2/Wide low voltage differential (LVD) small com-
puter system interface (SCSI) controller. This primary controller provides transfer
rates of up to 80 megabytes per second (MB/sec) with LVD hard-disk drives and
up to 40 MB/sec with non-LVD hard-disk drives. The chassis supports up to four
hard-disk drives of either type or a mix of both types.
Adaptec 7880 Ultra/Wide external and narrow internal SCSI controller. This sec-
ondary controller provides transfer rates of up to 40 MB/sec and is used for
removable media devices suc h as CD-ROM drives and tape drives. This controller
also supports up to 15 external SCSI devices through a 68-pin connector on the
computer’s back panel. The chassis supports up to three SCSI removable-media
devices.
NOTES: To achieve 80-MB/sec data transfer rates on the primar y SCSI channel, you
must use LVD hard-disk drives and either an LVD terminator or a multimode
terminator.
If you install a mix of LVD and non-LVD hard-disk drives, the system can only achieve
40-MB/sec data transfer rates for all SCSI drives. In addition, the LVD drives in this mix
must be capable of reverting to 40 MB/sec. In this configuration, you can terminate
the SCSI subsystem with either a single-ended or multimode terminator.
Dell ships multimode terminators only, regardless of system configuration.
The total length of the SCSI cable for the secondary SCSI channel is 2.5 meters (m)
for four attached devices.
The total number of SCSI devices connected to the secondary 7880 controller, both
internally and externally, cannot exceed 15.