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7 6 PCA-6181 User’s Manual
6.1 Introduction
The PCA-6181 is equipped with an Adaptec AIC-7899 single-chip PCI-
to-SCSI host adapter which provides a dual channel Ultra 160 multi-
tasking interface between your computer’s PCI bus and SCSI devices
(disk drives, CD-ROM drives, scanners, tape backups, removable
media drives, etc.). Ultra 160 is a new generation of SCSI technology
that expands SCSI performance from 80 MBytes/sec to 160 MBytes/
sec. Up to a total of 15 SCSI devices can be connected to each of the
SCSI connectors.
The AIC-7899 combines this Ultra 160 SCSI technology with
Adaptec’s SpeedFlex™ technology. SpeedFlex allows the Adaptec
SCSI card to be backwards compatible with previous generations of
SCSI products, while allowing newer Ultra 160 SCSI devices to operate
at the higher 160 MBytes/sec rate.
There are 3 SCSI connectors on the CPU card: CN50 and CN51 for
Ultra 160 devices, and CN52 for 50-pin SCSI devices. You can use
Ultra 160 and Ultra wide devices simultaneously without compromising
the performance.
If you need to configure the SCSI, the onboard SCSI Select configura-
tion utility allows you to change host adapter settings without opening
the computer or handling the board. The SCSI Select utility also
contains a utility to low-level format and verifies the disk media on
your hard disk drives.
Note: If any peripheral is running at SE mode, the
Ultra 160 SCSI segment will run at speeds up
to 40 MBytes/sec only instead of 160 MBytes/
sec.
6.2 Understanding SCSI
SCSI (pronounced “scuzzy”) stands for Small Computer Systems
Interface. SCSI is an industry standard computer interface for connect-
ing SCSI devices to a common SCSI bus.
A SCSI bus is an electrical pathway that consists of a SCSI interface