| In October, Intel introduced a new interrupt
architecture designed to improve multitasking performance
and pave the way for multiprocessing operating systems,
such as the unreleased Windows NT. The architecture has
been adopted by major hardware and software companies and
is expected to begin appearing in computers late this year
or early in 1993. At the very heart of the architecture is a new interrupt controller chip, the Intel 82489DX. It supersedes the 8259A, which made its debut in 1978 and is found in almost all PC compatibles. The 8259A has no support for multitasking or multiprocessing, although it can be tricked by software to accommodate the kind of cooperative multitasking used in Windows 3.1. Intel says that the 8259A has been rendered obsolete by the arrival of more sophisticated operating systems that will allow true preemptive, multithreaded multitasking and symmetric multiprocessing. Operating systems such as Windows NT, OS/2 2.0, Solaris 2.0, NextStep 486, and Unix System V must have a more robust interrupt architecture to handle their demands. Computers that are built around the 82489DX can have as many as 255 microprocessors, each with its own interrupt controller. In a symmetric multiprocessing environment (e.g., Windows NT), the controllers automatically assign a task to the least busy processor in the system or to the processor running the lowest priority task. This ensures that processing loads are distributed equally among all processors in the system. The 82489DX connects directly to the high-speed CPU bus rather than communicating with the CPU over the slower I/O bus, as the old controller did. Also, the 82489DX runs at 50 MHz, compared to the older chip's 8 MHz. Intel says these improvements boost performance by 5 or 6 MIPS on a 100-MIPS desktop computer or by 20 to 25 MIPS on a 100-MIPS network server (which handles many more interrupts from clients on the network). Intel says future versions of the controller will run at the same speeds as its fastest CPUs. Companies adopting the new architecture include IBM, Microsoft, DEC, Novell, NCR, Sunsoft, NEC, Acer, AST, Everex, Olivetti, The Santa Cruz Operation, Sequent, and USL. Copyright 1994-1997 BYTE |