Apple Macintosh LC - Manual (Page 131)

CHAPTER 16-EXPANDING YOUR MACINTOSH SYSTEM
Your Macintosh computer is the heart of a powerful and versatile system. This
system can include such external devices as disk and tape drives, printers, a
scanner, a modem, a graphics tablet, and audio devices. All of these devices
can be connected to the computer when it is originally set up or added later
to expand its power.
The internal memory of your Macintosh computer can be expanded from the
standard amount of memory, 2 megabytes (MB), to as much as 10 MB. This
additional memory must be installed by an authorized Apple dealer.
This chapter provides an overview of the components most commonly used with
the Macintosh. When you are connecting a specific device to your Macintosh,
be sure to follow the detailed instructions provided with the device.
Connecting SCSI devices
The Macintosh LC has a port for connecting devices that use the Small
Computer System Interface (SCSI). The SCSI port permits high-speed
communication between the computer and the device. (SCSI is usually
pronounced "skuh-zee.")
Among the SCSI devices commonly used with the Macintosh are hard disk drives,
tape backup drives, CD-ROM (compact disc read-only memory) drives, scanners,
and certain printers.
Because SCSI devices can be connected to one another, or daisy-chained,
rather than having to be connected directly to the computer, the Macintosh
can support more than one SCSI device. Up to seven SCSI devices can be linked
to the Macintosh in a daisy chain.
!! WARNING: Always switch off the computer and all components before adding
or removing any part of the system. If you add or remove a component or its
cable while the equipment is on, you may damage the Macintosh, the component,
or both. !!
Setting the SCSI device number
Each SCSI device comes with a preset ID number from 0 to 7, which you can
change if necessary. At the factory Apple assigns a number to each type of
SCSI device it manufactures; in most instances, you should not need to
change the number unless two of the devices in your system have the same
number.
The Macintosh uses the SCSI ID number to assign each device a priority in a
chain of SCSI devices. The higher the number, the higher the device's
priority; the computer itself is number 7 (so nothing else can have that
number). The devices you use most often should have the highest priority
numbers. (An exception to this rule is the internal hard disk, if your
Macintosh LC has one, which is set to 0 at the factory.)
!! WARNING: Be sure to change the ID number of one device if you have two
SCSI devices with the same ID number. You could lose information on one or
both devices if you try to use two SCSI devices with the same ID number. !!
Follow these steps to change the SCSI ID number of an Apple SCSI device: