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Glossary 31
Glossary
G
Glossary
Address - A specific location in memory, designated either numerically or by a symbolic
name.
Asynchronous Data Transfer - A method of transmission which does not require a common
clock, but separates fields of data by stop and start bits. It is slower than synchronous data
transfer.
BIOS - Basic Input/Output System. Software that provides basic read/write capability. Usually
kept as firmware (ROM based). The system BIOS on the mainboard of a computer is used to
boot and control the system. The SCSI BIOS on your host adapter acts as an extension of the
system BIOS.
Bit - A binary digit. The smallest unit of information a computer uses. The value of a bit (0 or
1) represents a two-way choice, such as on or off, true or false, and so on.
Bus - A collection of unbroken signal lines across which information is transmitted from one
part of a computer system to another. Connections to the bus are made via taps on the lines.
Bus Mastering - A high-performance way to transfer data. The host adapter controls the
transfer of data directly to and from system memory without bothering the computer’s
microprocessor. This is the fastest way for multitasking operating systems to transfer data.
Byte - A unit of information consisting of eight bits.
Chain - A topology in which every processor is connected to two others, except for two end
processors that are connected to only one other.
CISPR - A special international committee on radio interference (Committee, International
and Special, for Protection in Radio). B-2 Glossary of Terms and Abbreviations
Configuration - Refers to the way a computer is set up; the combined hardware components
(computer, monitor, keyboard, and peripheral devices) that make up a computer system; or
the software settings that allow the hardware components to communicate with each other.
CPU - Central Processing Unit. The “brain” of the computer that performs the actual
computations. The term Micro Processor Unit (MPU) is also used.
DMA - Direct Memory Access. A method of moving data from a storage device directly to
RAM, without using the CPU’s resources.
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 processor is in
control and the flow is by byte.
Device Driver - A program that allows a microprocessor (through the operating system) to
direct the operation of a peripheral device.
Differential - A hardware configuration for connecting SCSI devices. It uses a pair of lines
for each signal transfer (as opposed to single-ended SCSI which references each SCSI signal
to a common ground).
Dword - A double word is a group of 4 consecutive bytes or characters that are stored, addressed,
transmitted, and operated on as a unit. The lower two address bits of the least significant byte
must equal zero in order to be dword aligned.
EEPROM - Electronically-Erasable Programmable Read Only Memory. A memory chip
typically used to store configuration information. See NVRAM.