Intel 486

Intel 486

(Or "i486", "iAPX 80486", and "Intel DX4" but usually just "486"). A range of Intel CISC microprocessors which is part of the Intel 80x86 family of processors.

The 486s are very similar to their immediate predecessor, the Intel 80386DX. The main differences are that the 486 has an optimised instruction set, has an on-chip unified instruction and data cache, an optional on-chip floating-point unit (FPU), and an enhanced bus interface unit. These improvements yield a rough doubling in performance over an Intel 80386 at the same clock rate.

There are several suffixes and variants including:

Intel 486SX - a 486DX with its FPU disabled (see crippleware).

Intel 486DX - 486SX with a working FPU.

486DX-2 - runs at twice the external clock rate.

486SX-2 - runs at twice the external clock rate.

486SL - 486DX with power conservation circuitry.

486SL-NM - 486SX with power conservation circuitry; SL enhanced suffix, denotes a 486 with special power conservation circuitry similar to that in the 486SL processors.

487 - 486DX with a slightly different pinout for use in 486SX systems.

OverDrive - 486DX-2 with a slightly different pinout for use in 486SX systems.

RapidCAD - 486DX in a special package with a companion FPU dummy package for use in Intel 80386 systems.

Intel DX4, Cyrix Cy486SLC.

External clock rates include 16MHz, 20MHz, 25MHz, 33MHz, 40MHz, although 16Mhz is rare now, and the 20MHz processors are often clock doubled.

The 486 processor has been licensed or reverse engineered by other companies such as IBM, AMD, Cyrix, and Chips & Technologies. Some are almost exact duplicates in specications and performance, some aren't.

The successor to the 486 is the Pentium.
This article is provided by FOLDOC - Free Online Dictionary of Computing (
References in periodicals archive ?
Towards the end of the '80s, Intel unveiled the Intel 486 processor, with 1.2 million transistors - by far the most advanced microprocessor at that time.
The computer and software run on an old Intel 486 chip, technology that became obsolete after the introduction of the Windows 95 operating system.
The duo used commodity Intel 486 DX4/100 processors with a 10 MB per second Ethernet network, combined with the Linux operating system, to create the first commodity-based cluster.
l System requirements: Windows 95, 98, NT 4.0 or higher, Intel 486 66Mhz, 64Mbyte of RAM, 2x CD ROM.
While the MH-47D now has a single Intel 486 processor in each control display unit, CAAS draws on one Power PC 750 processor in each control display unit and two Power PC 750 processors in each multi-function display.
A transition to a new computer that is backward compatible with a previous computer, such as that from the Intel 486 to the Pentium, need not constitute a new generation.
In layman's terms, a 12.5 MTOPS computer was a commonly available machine running on the now-ancient Intel 486 chip.
1993 -- The Pentium[R] processor -- five times the performance of the Intel 486 -- is introduced.
The first Beowulf linked 16 Intel 486 processors (100 MHz) with standard Ethernet (10 megabits/sec) and performed 50 megaFLOPS on applications, about 1/20th of the initial goal.
It takes at least an Intel 486 chip to run Microsoft Internet Explorer 4.0 or the latest browser and e-mail software from Netscape.
You may add a 20x CD-ROM drive to your old Intel 486, and the video will still be ar worse than from a 12x CD-ROM drive with a 166-MHz Pentium.
As recently as 1991, a PC based on the Intel 486 processor cost about $223 per million instructions per second (MIPS) of performance.