Specifications

Glossary
113
microprocessor to jump to a special program called the interrupt service routine. The
microprocessor executes this special program, which normally involves servicing the
interrupting device. When the interrupt service routine is completed, the
microprocessor resumes execution of the program it was working on before the
interruption occurred.
ISR
(Interrupt Service Routine) A program executed by the microprocessor upon receipt
of an interrupt request from an I/O device and containing instructions for servicing
of the device.
Jumper
A set of male connector pins on a circuit board over which can be placed coupling
devices to electrically connect pairs of the pins. By electrically connecting different
pins, a circuit board can be configured to function in predictable ways to suit
different applications.
KB or KByte
(Kilobyte) Approximately one thousand bytes. 2
10
= 1024 bytes exactly.
Logical
Address
The memory-mapped location of a segment after application of the address offset to
the physical address.
LBA
(Logical Block Addressing) A method the system BIOS uses to reference hard disk
data as logical blocks, with each block having a specific location on the disk. LBA
differs from the CHS reference method in that the BIOS requires no information
relating to disk cylinders, heads, or sectors. LBA can be used only on hard disk drives
designed to support it.
MB or
MByte
(Megabyte) Approximately one million bytes. 2^20 = 1,048,576 bytes exactly.
Memory
A designated system area to which data can be stored and from which data can be
retrieved. A typical computer system has more than one memory area. See
Conventional Memory and Extended Memory.
Memory
shadowing
Copying information from an extension ROM into DRAM and accessing it in this
alternate memory location.
Offset
The difference in location of memory-mapped data between the physical address and
the logical address.
Operating
System
See DOS.
PMC
(PCI Mezzanine Card) A new standard form factor for PCI add-in modules. PMCs
mate with their respective connectors on the motherboard and are secured with
screws.
PCI
(Peripheral Connect Interface) A popular microcomputer bus architecture standard.
Peripheral
Device
An external device connected to the system for the purpose of transferring data into
or out of the system.
PC/AT
(Personal Computer/Advanced Technology) A popular computer design first
introduced by IBM in the early 1980s.
PS/2
(Personal System 2) Computers designed with IBM’s proprietary bus architecture
known as Micro Channel.