10 GlossaryIRQInterrupt Request. A signal that, when received by the CPU, makes it stop what it isgoing to do something else. An interrupt is a way in which a particular device in acomputer communicates with the CPU. PCs have 16 IRQ lines that can be assignedto different devices (for example, printers, scanners, modems). No two devices canhave the same IRQ address. See interrupt.ISAIndustry Standard Architecture. The bus architecture used in the IBM PC/XT andPC/AT. The AT version of the bus is called the AT bus and has become an industrystandard. The apparent successor is the PCI local bus architecture found in most oftoday’s computers. Most modern computers include both an AT bus for slowerdevices and a PCI local bus for devices that need better bus performance. In 1993,Intel and Microsoft introduced a new version of the ISA specification called Plugand Play ISA. Plug and Play ISA enables the operating system to configureexpansion boards automatically so that users do not need to fiddle with DIPswitches and jumpers. See plug and play.isochronousA form of data transmission in which individual characters are only separated by awhole number of bit-length intervals.Kkilobyte(KB) 1024 bytes.LL2 cacheRefers to “level 2” or “secondary” cache. A type of cache that resides on themotherboard except when referring to a Pentium II machine, where it resides on theCPU module.LANLocal Area Network.LPT1Name assigned to the parallel port by the Windows operating system. A secondparallel device is assigned LPT2 (if there is another parallel port). Also called theprinter port.MmasterPart of a two-sided communication that initiates commands (to a “slave” thatcarries out the commands).megabyte(MB) 1,048,576 bytes.
