14 Chapter 5 : Connecting Hard Disk Drives14 Chapter 5 : Connecting Hard Disk Drives14 Chapter 5 : Connecting Hard Disk Drives
Choosing a hard disk
If you plan to buy a hard disk that is not listed on the supplied card, the following
specifications should be checked first.
SCSI
For an general introduction to SCSI, see “SCSI” on page3.
Setting up a SCSI daisy chain requires a little more than just making connections. SCSI
devices require ID numbers and the daisy chain must be terminated correctly. These are
explained in the following three sections, “SCSI cables”, “SCSI ID setting”, and “SCSI
termination”.
When using a SCSI daisy chain, the following points should be borne in mind.
• Allocate each device its own SCSI ID number.
• Terminate the SCSI bus correctly.
• Use quality cables and keep the length down.
• Use the little wire clips (or screws) on a SCSI connector to fasten the cable plugs
securely.
• All devices connected in the daisy chain must be switched on to use the system.
• Never switch off, or disconnect a device once the system has been switched on.
Specification Check Notes
Is it compatible with your computer? Maybe it is advertised as compatible, or your
dealer recommends it.
Does it have two SCSI connectors? You need two to continue the SCSI daisy chain.
Are the SCSI connectors 25-pin
D-SUB, or 50-way Amphenol?
Macintosh computers are fitted with a 25-pin
D-SUB connector, while most other SCSI devices
have a 50-way Amphenol connector.
Are the SCSI cables supplied? If not, you will need to purchase them separately.
Can the SCSI ID be set from 0 ~ 7? (for
Macintosh you only need 0 ~ 6)
If not, it might clash with another device’s ID, in
which case you may have to rearrange the ID
numbers of some other SCSI devices in the
chain.
Does it have internal or external
termination?
External terminators are normally connected to
the rear of the SCSI device. If the device has an
internal terminator, make sure it can be switched
off so that any device can be positioned at the
end of the SCSI daisy chain.
Access Time?
Measured in milliseconds, this is an indication of
how fast data from different areas of the disk can
be retrieved. The maximum we recommend is
30ms. An access time slower than this may affect
the performance of the CBX-D5.
Data Transfer Rate?
Usually measured in Megabits per second
(Mbit/s), this shows how fast data can be written
to and read from the hard disk. The minimum we
recommend is 16Mbits/s. A transfer rate less than
this may affect the performance of the CBX-D5.
NOTE: Switch off all your equipment before making any SCSI connections.