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.
References in periodicals archive ?
Towards the end of the '80s, Intel unveiled the Intel 486 processor, with 1.
0 or higher, Intel 486 66Mhz, 64Mbyte of RAM, 2x CD ROM.
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.
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.
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For now, SoundQuest customers will need a PC with at least 16 megabytes of memory, a microprocessor with at least the power of an Intel 486, a sound card and speakers.
As recently as 1991, a PC based on the Intel 486 processor cost about $223 per million instructions per second (MIPS) of performance.
Many of the enterprisewide scheduling systems support the Intel 486 client platform (68.
The chip maker said more Intel 486 users will be able to upgrade to Pentium processor technology since the new processor serves the largest share of the Intel486 market.
The fifth-generation processor, the Pentium, 66 MHz with a 64-bit databus and a 32-bit instruction set, runs up to five times the speed of the Intel 486 DX-33 CPU, enabling advanced image processing--of great importance in many desktop publishing applications, particularly those involving fine gradations of gray scales and process colors.
It is true that graphics productivity will run much faster on Macintosh systems that use PowerPC processors than they do now on personal computers that use Motorola 680x0 or Intel 486 chips.