HP Ultra320 A7173A manual Glossary, Bit

Glossary

A
address	A specific location in memory, designated either numerically or by a symbolic name.
asynchronous	One of the ways data is transferred over the SCSI bus. It is slower than synchronous data
data transfer	transfer.
B
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.
Boot Console	Provides, among other things, the reading and setting of SCSI parameters without the OS
Handler (BCH)	running.
bus	A collection of wires in a cable or copper traces on a circuit board used to transmit data, status,
	and control signals. EISA, PCI, and SCSI are examples of buses.
bus mastering	A high-performance way to transfer data. The host bus adapter controls the transfer of data
	directly to and from system memory without bothering the computer’s microprocessor. This
	is the fastest way for multi-tasking operating systems to transfer data.
byte	A unit of information consisting of eight bits.
C
central processing	The “brain” of the computer that performs the actual computations. The term Micro Processor
unit (CPU)	Unit (MPU) is also used.
chain	A topology in which every device is connected to two others, except for two-end devices that
	are connected to only one other.
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.
Cyclic	32-bit scheme (referred to as CRC-32) included in Ultra320 that ensures complete integrity of
Redundancy	the transferred data. CRC is guaranteed to detect all single bit errors, any two bits in error, or
Check (CRC)	any combination of errors within a single 32-bit range.
D
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).
direct memory	A method of moving data from a storage device directly to RAM, without using the CPU’s
access (DMA)	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 flow is byte by byte.
Domain	A software procedure in which a host system queries a device to determine the device’s ability
Validation	to communicate at the data transfer rate that was negotiated.

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