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

Glossary
port address
Glossary120
port address Also port number. The
address through which commands are sent
to a host bus adapter. This address is
assigned by the PCI bus.
port number See port address.
Processor Dependent Code (PDC) The
system firmware on HP PA-RISC systems. It
provides basic read/write capability. Usually
kept as firmware (ROM based). The system
firmware on the main board of a computer is
used to boot and control the system.
programmed input/output (PIO) A way
the CPU can transfer data to and from
memory via the computer’s I/O ports. PIO
can be faster than DMA, but requires CPU
time.
Q
queue tags A way to keep track of multiple
commands while allowing increased
throughput on the SCSI bus.
R
Random Access Memory (RAM) In
general, the computer’s primary working
memory in which program instructions and
data are stored and are accessible to the
CPU. Information can be written to and read
from RAM. The contents of RAM are lost
when the computer is turned off.
Read-Only Memory (ROM) Memory from
which information can be read but not
changed. The contents of ROM are not
erased when the computer is turned off.
Reduced Instruction Set Computer
(RISC) core The HBA’s SCSI chips contain
a RISC processor, programmed through
microcode scripts.
S
SCSI bus A host bus adapter and one or
more SCSI peripherals connected by cables
in a linear chain configuration. The host bus
adapter can exist anywhere on the chain,
allowing connection of both internal and
external SCSI devices. A system can have
more than one SCSI bus by using multiple
host bus adapters.
SCSI device Any device conforming to the
SCSI standard that attaches to the SCSI bus
by means of a SCSI cable. This includes
SCSI host bus adapters and SCSI
peripherals.
SCSI ID A unique identification for each
SCSI device on the SCSI bus. Each SCSI bus
has fifteen available SCSI IDs numbered 0
through 15 for Wide SCSI or 0-7 for 8-bit
SCSI. The host bus adapter is usually
assigned ID 7, which gives it priority to
control the bus.
SCSI-2 The SCSI specification that adds
features to the original SCSI-1 standard.
SCSI-3 The current SCSI specification,
which adds features to the SCSI-2 standard.
single-ended (SE) SCSI A hardware
specification for connecting SCSI devices. It
references each SCSI signal to a common
ground, as opposed to differential SCSI and
low-voltage differential SCSI, which use a
separate return for each signal.