SCSI Connections

SCSI Bus Differences

SCSI Bus Differences

A Small Computer Systems Interface (SCSI) bus is an IEEE standard bus for connecting your workstation to internal and external devices (SCSI devices) running at different speeds, singly or in combination. Examples of these SCSI devices are 4-mm DDS-format tape drives, CD-ROM drives, and Win- chester hard disk drives.

There are two types of SCSI buses available with this workstation - a nar- row, single-ended SCSI bus (SE SCSI), and a fast, wide differential SCSI bus (FWD SCSI) (on C160/C180/C200-upgrade), or an ultra wide single- ended SCSI bus (Ultra Wide-SE) (C200/C240 only). Table 19 shows the specification differences between these SCSI buses, and Table 20 shows the SCSI addresses, ID numbers, and arbitration priorities for each.

CAUTION:Do not mix single-ended and fast, wide devices on any one bus type. Doing this will

 

 

 

cause a system failure.

 

 

 

Table 19

 

SCSI Bus Differences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Data Bus

Maximum

Maximum

Device

Controller

 

Transfer Rate

 

Physical

Embedded

 

 

Width

Addresses*

Cable Length

 

 

 

Location

or Plugable

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Narrow Single-

 

 

 

 

 

 

 

Ended

 

8 bits

8

6.0 meters

Internal and

Embedded

 

 

 

 

Up to 5 Mbytes

 

 

 

(19.6 feet)

external

 

 

per second

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fast, Wide Dif-

 

 

 

 

 

 

 

ferential

 

16 bits

16

25 meters

Internaland

Embedded

 

 

 

 

Up to 20 Mbytes

 

 

 

(82 feet)

external

 

 

per second

 

 

 

 

 

 

 

 

 

 

 

 

 

 

153