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Glossary 33
Glossary
NVRAM - Non Volatile Random Access Memory. Actually an EEPROM (Electronically-
Erasable Programmable Read Only Memory chip) used to store configuration information.
See EEPROM.
Operating System - A program that organizes the internal activities of the computer and its
peripheral devices. An operating system performs basic tasks such as moving data to and
from devices, and managing information in memory. It also provides the user interface.
Parity Checking - A way to verify the accuracy of data transmitted over the SCSI bus. One
bit in the transfer is used to make the sum of all the 1 bits either odd or even (for odd or even
parity). If the sum is not correct, an error message appears.
PCI - Peripheral Component Interconnect. A local bus specification that allows connection of
peripherals directly to computer memory. It bypasses the slower ISA and EISA busses.
Peripheral Devices - A piece of hardware (such as a video monitor, disk drive, printer, or
CD-ROM) used with a computer and under the computer’s control. SCSI peripherals are
controlled through a SCSI host adapter.
Pin-1 Orientation - The alignment of pin-1 on a SCSI cable connector and the pin-1 position
on the SCSI connector into which it is inserted. External SCSI cables are always keyed to
insure proper alignment, but internal SCSI ribbon cables are sometimes not.
PIO - Programmed Input/Output. A way the CPU can transfer data to and from memory via
the computer’s I/O ports. PIO is usually faster than DMA, but requires CPU time.
Port Address - Also Port Number. The address through which commands are sent to a host
adapter board. This address is assigned by the PCI bus.
Port Number - See Port Address.
Queue Tags - A way to keep track of multiple commands that allows for increased throughput
on the SCSI bus.
RAM - Random Access Memory. 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.
RISC Core - ASUS SCSI chips contain a RISC (Reduced Instruction Set Computer) processor,
programmed through microcode scripts.
ROM - Read Only Memory. Memory from which information can be read but not changed.The
contents of ROM are not erased when the computer is turned off.
SCAM - SCSI Configured AutoMatically. A method to automatically allocate SCSI IDs via
software when SCAM compliant SCSI devices are attached.
SCSI - Small Computer System Interface. A specification for a high performance peripheral
bus and command set. The original standard is referred to as SCSI-1.
SCSI-2 - The current SCSI specification which adds features the original SCSI-1 standard.
SCSI-3 - The next SCSI specification, which adds features to the SCSI-2 standard. Although
this version is still in development, parts of the SCSI-3 standard are already in use.
SCSI Bus - A host adapter and one or more SCSI peripherals connected by cables in a linear
chain configuration. The host adapter may exist anywhere on the chain, allowing connection
of both internal and external SCSI devices. A system may have more than one SCSI bus by
using multiple host adapters.
SCSI Device - Any device that conforms to the SCSI standard and is attached to the SCSI bus
by a SCSI cable. This includes SCSI host adapters and SCSI peripherals.