BusLogic BT-956C, User Manual

Cable length should follow the SCSI specification. Where the data transfer

rate is 

 the cable should be no more than 20 feet long; where the

data transfer rate is 10 

 it should be no longer than 10 feet. Where

both   and 

 devices are connected to the same channel, the cable

should be less than 10 feet for a 10 

 data transfer rate. In addition,

drives should be equally distributed on each channel for best performance.

Termination settings on your Wide SCSI host adapter are as follows:

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Low Byte 

terminates data bits O-7.

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High Byte 

terminates data bits 8-15.

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Low Byte 

and 

High Byte 

together 

(default) 

terminate all signals.

Table 2-l indicates what your Low Byte and High Byte settings should be

based on the connector and the attached devices 

 or 

Setting the SCSI Device ID

Each SCSI device is assigned a unique SCSI ID ranging from 0 through 7

for 

 devices, or 0 through 15 for 

 devices. Most SCSI peripheral

devices are shipped with a preassigned SCSI ID number. Your 

adapter is by default 

SCSI ID 7.

If you need to change the SCSI ID for a peripheral device refer to the in-

structions in its owner’s manual. A SCSI ID jumper or switch is usually lo-

cated on the peripheral’s back panel.

Table 2-1. Termination Options

External

Internal

Connector Connector

8-bit On On

Select if the adapter is 
ured at the end of the SCSI

On On

chain using only one of the 

 On On

On

Select if the adapter is in the
middle of a SCSI chain, but is

configured with one 

 and

one 

 connector. Termina-

tion is required on the cable
ends or on the devices at the
ends of the cable.

The only time you may need to change the adapter’s SCSI ID is when mul-

tiple adapters share the same SCSI bus. To change your adapter SCSI ID

use the Host 

Adapter SCSI ID 

option on the 

 Configuration

Menu (Section 3, “Using the 

 Utility”).

Off

On

Note: BIOS looks for the boot drive by scanning devices according to their 

ID, starting at 

 ID 0. If your boot drive is at a higher number than another

drive, BIOS will boot from the other drive. In this case, you need to change the

 ID of the desired boot drive to a lower value.

Off

Off

No termination 

is required if the

adapter is in the middle of the
SCSI chain using two 
connectors with 

 devices.

Off

On

High Byte must be 

On 

if the

adapter is in the middle of the
SCSI chain using two 68-pin
connectors with one attached to

 devices 

only.

Terminating SCSI Devices

Terminators are required for reliable operation of the SCSI bus. The first

and last SCSI devices connected together on a SCSI bus must have termi-

nators installed or enabled. Terminators can be connected to either the

SCSI device itself or affixed to the SCSI cable ends.

Note the following:

This table assumes that you would use the 50-pin connector to connect

internal 

 devices and, therefore, does not include settings for 

devices on the internal 

 connector.

When 

 and 

 devices are mixed on the cable attached to a 

pin connector, you still need to terminate all signals.

Where you are installing mixed devices (i.e., 

 and 

 devices), ter-

mination is a little more complicated. Even where the host adapter is in the

middle 

of the SCSI chain, there are configurations where you may still have

to turn on termination on the adapter itself, in addition to the terminators

on both ends of the chain.

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installation

Installation 

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