AMM-1570/1572 User’s Guide
Stock Number:510526-00, Rev. B Page:Glos sary-9
Print Spec Number: 492379-00
Current Date: 3/7/94 ECN Date: 3/8/94
Glossary-9
Glossary
Single-threaded Operation
Operation of the computer sys-
tem such that only one program
can be operating or active at a
time. The system must wait until
all resources are available before
starting an operation, and it can-
not start another operation until
the first one is completed.
Small Computer Systems Interface
See SCSI
Synchronous Data Transfer
A method of data transfer in
which data on the SCSI bus is
clocked with fixed-length, fixed-
frequency strobe pulses. The
acknowledgments may be
delayed several clock periods
from the data requests. Synchro-
nous data transfer can be used
only for data transmission on
the SCSI bus. It cannot be used
forC ommand, Message, and
Status transmission.
Synchronous Data Transfer Negotiation
The message exchange between
the initiator and the target that
allows the negotiation of the
data transfer frequency and
delay between requests and
acknowledgments required for
synchronous data transfer. Once
negotiated, synchronous data
transfer parameters remain
unchanged until certain
reinitialization activities occur.
Tagged Queuing
A SCSI-2 feature that allows the
SCSI device to queue return data
commands in a different order
than requested by the SCSI host
adapter, thereby increasing
performance.
Target (or Target Device)
A SCSI device that performs an
operation requested by an initia-
tor. The target may be a periph-
eral device, such as a disk drive
performing a service for an initi-
ator. The target may also be a
host adapter performing a
processor-type device service for
an initiator.
Termination
A physical requirement of the
SCSI bus. The devices at the
physical ends of the SCSI bus
must have terminating resistors
either installed or enabled;
devices in the middle of the bus
must have terminating resistors
either removed or disabled.
VL-Bus
The VESA local-bus developed
by the Video Electronics Stan-
dard Association to provide a
high-speed local-bus for high-
performance peripherals within
a computer system.
Word
A 2-byte (16-bit) unit of data.
Zero Latency Reads
A method of minimizing
mechanical limitations of fixed
disks by requesting data in an
unordered sequence. The data is
reordered by the host adapter.
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