Specifications

Glossary-3
Glossary
APA-1460 SlimSCSI Technical Reference
Stock Number: 510671-00 Rev. A Page: -3
Print Spec Number: 492966-00
Current Date: 8/22/94 ECN Date: 8/30/94
ware to request the services of the host
adapter in transferring information to and
from peripheral devices attached to the
host adapter.
Host Adapter
A printed circuit board or integrated circuit
that installs in a standard microcomputer
system and provides a SCSI bus connection
so that SCSI devices can be connected to
the microcomputer.
I
IBM
®
PC-AT
®
Compatible
Any computer that emulates exactly the
IBM PC-AT and uses an ISA backplane bus.
Industry Standard Architecture
See ISA.
Initiator
A SCSI device that requests an operation to
be performed by another SCSI device (the
target). The initiator provides all the com-
mand information and parameters required
to perform the operation, but the target car-
ries out the details of the operation. The
host adapter is usually called the initiator;
other devices on the SCSI bus, such as disk
drives, are called SCSI targets.
Interrupt Request Channel
See IRQ.
IRQ
Interrupt Request Channel. An electrical
channel through which a hardware device
can send a message to get the immediate
attention of the computer’s Central Pro-
cessing Unit (CPU).
ISA
Industry Standard Architecture. The type
of computer bus used in most computers.
An ISA bus enables expansion devices such
as network cards, video adapters, and
modems to send data to and receive data
from the computer’s CPU and memory
either 8 bits or 16 bits at a time. Expansion
devices are plugged into sockets in the
computer motherboard. ISA is sometimes
called the AT bus, because it was first used
in the IBM PC/AT.
K
KByte
Kilobyte. A measure of computer storage.
One KByte equals 1024 bytes. (A byte is the
amount of storage needed to hold one
character.)
L
Logical Drive
A computer disk storage device that can be
addressed as a specific drive letter, such as
C or D. A single physical disk device, such
as a hard disk drive, can be partitioned into
two or more logical drives with different
drive letters.
Logical Unit
A device that is addressed when an initia-
tor (usually the host adapter) sends a Read
or Write command to a target. For example,
a tape drive is a target and the tape car-
tridge in the drive is the Logical Unit (LU).
Most SCSI targets have only one LU; a sin-
gle SCSI target can have up to eight LUs.
Logical Unit Number
An encoded 3-bit identifier for a logical
unit.
LU
See Logical Unit.
LUN
See Logical Unit Number.
M
MByte
Megabyte. A measure of computer storage.
One MByte equals 1,048,576 bytes. (A byte
is the amount of storage needed to hold one
character.)
O
Operating System
The software that controls the basic opera-
tion of the host computer. Examples are
MS-DOS
®
, UNIX
®
and Netware.
OS
See Operating System.