HP A6829A PCI Dual Channel Ultra160 SCSI Host Bus Adapter Service and User Guide (May 2003)

Glossary
DMA bus master
Glossary118
DMA bus master A feature that allows a
peripheral to control the flow of data to and
from system memory by blocks, as opposed
to PIO (Programmed I/O), where the flow is
byte by byte.
Domain Validation A software procedure
in which a host system queries a device to
determine the device’s ability to
communicate at the data transfer rate that
was negotiated.
E
electronically erasable programmable
read-only memory (EEPROM) A memory
chip typically used to store configuration
information. See Non-Volatile Random
Access Memory (NVRAM).
external SCSI device A SCSI device
installed outside the computer cabinet.
External SCSI devices are connected in a
chain using shielded cables.
F
Fast SCSI A standard for SCSI data
transfers. It allows a transfer rate of up to 10
MBytes/sec over an 8-bit SCSI bus, and up to
20 MBytes/sec over a 16-bit SCSI bus.
FCC Federal Communications Commission.
firmware Software that is permanently
stored in ROM. In the case of PDC, it can be
accessed during boot time without the aid of
an operating or file system.
H
hard disk A rigid disk permanently sealed
into a drive cartridge. A hard disk can store
very large amounts of information.
host The computer system in which a SCSI
host bus adapter is installed. It uses the
SCSI host bus adapter to transfer
information to and from devices attached to
the SCSI bus.
host bus adapter (HBA) A circuit board
and/or integrated circuit device that
provides a SCSI bus connection to the
computer system.
I
internal SCSI device A SCSI device
installed inside the computer cabinet. These
devices are connected in a chain using an
unshielded ribbon cable.
interrupt request channel (IRQ) A path
through which a device can get the
immediate attention of the computer’s CPU.
The PCI bus assigns an IRQ path for each
SCSI host bus adapter.
K
KByte (kilobyte) A measure of computer
storage equal to 1024 bytes.
L
logical unit A subdivision, either logical or
physical, of a SCSI device. Most devices have
only one logical unit, but up to sixteen are
allowed for a 16-bit SCSI bus and eight for
an 8-bit SCSI bus.
logical unit number (LUN) An encoded
three-bit number for the logical unit.