Editing Intel DX2 (section)

{{Short description|Clock-doubled i486}}
{{Multiple issues|
{{refimprove|date=June 2024}}
{{original research|date=December 2014}}
}}

[[File:80486dx2-large.jpg|thumb|i486DX2 CPU core]]
The '''Intel486 DX2''',<ref>Hodson, Gerri, "The Intel486 DX2 Microprocessor: Speed-Doubler Technology", Intel Corporation, Microcomputer Solutions, May/June 1992, page 2-5</ref> rumored as '''80486DX2''' (later rebadged '''i486DX2'''), is a [[central processing unit|CPU]] produced by [[Intel]] that was first introduced in 1992. The i486DX2 was nearly identical to the [[Intel 80486DX|i486DX]], but it had additional [[clock multiplier]] circuitry. It was the second CPU [[integrated circuit|chip]] to use [[CPU multiplier|clock doubling]], whereby the processor runs two internal logic [[clock cycle]]s per external bus cycle. An i486 DX2 was thus significantly faster than an i486 DX at the same bus speed thanks to the 8K on-chip cache shadowing the slower clocked external bus. Both 25/50 and 33/66&nbsp;MHz Intel486 DX2 CPU uses the [[800 nm process]] technology.<ref>Intel Corporation, "Coming Attractions: Clock-Doubling Technology", Microcomputer Solutions, January/February 1992, page 6</ref> With the internal clock doubler CPU, it boosts overall system performance between 50 and 70 percent above the original Intel486 DX series.<ref>Intel Corporation, "A Guide to the Intel Architecture", Microcomputer Solutions, January/February 1992, page 11</ref>  In other words, the 50-MHz Intel486 DX2 provides about 70 percent improvement over the 25-MHz Intel486 and about 30-percent improvement over the 33-MHz Intel486 CPU.  The 50-MHz Intel486 DX2 CPU was rated at 40 Dhrystone MIPS.<ref>Hodson, Gerri, "The Intel486 DX2 Microprocessor: Speed-Doubler Technology", Intel Corporation, Microcomputer Solutions, May/June 1992, page 2-5</ref>  The 66-MHz Intel486 DX2 version performed 54 ([[Dhrystone]] V1.1) [[Instructions_per_second#Millions_of_instructions_per_second_(MIPS)|MIPS]].<ref>Intel Corporation, "New Product Focus: OEM: Speed-Doubling Technology Powers Intel486 DX2 66-MHz CPU", Microcomputer Solution, November/December 1992, Page 18</ref>

The i486DX2-66 was a very popular processor for [[video game]]s enthusiasts in the early to mid-90s. Often coupled with 4 to 8 [[megabyte|MB]] of RAM and a [[VESA Local Bus|VLB]] video card, this CPU was capable of playing virtually every game title available for years after its release, right up to the end of the [[MS-DOS]] game era, making it a "sweet spot" in terms of CPU performance and longevity. The introduction of 3D graphics spelled the end of the 486's reign, because of their heavy use of [[floating point]] calculations and the need for faster [[CPU cache|cache]] and more [[memory bandwidth]]. Developers began to target the [[P5 (microarchitecture)|P5]] [[Pentium (brand)|Pentium]] processor family almost exclusively with [[x86 assembly language]] optimizations which led to the usage of terms such as ''[[Pentium compatible processor]]'' for software requirements. An i486DX2-50 version was also available, but because the bus speed was 25&nbsp;MHz rather than 33&nbsp;MHz, this was a significantly less popular processor.

There are two major versions of the DX2 - Identified by P24 and P24D, the latter has a faster [[CPU cache|L1 cache]] mode, called "[[Cache (computing)#WRITE-BACK|write-back]]", that improves performance. The original P24 version offered only the slower "write-through" cache mode. [[Am486|AMD]] and [[Cyrix]] both produced a competitor for the Intel i486DX2.

The 50-MHz Intel486 DX2 were available in production volumes for US$550 each in 1,000-pieces quantities at the time of the press.<ref>Hodson, Gerri, "The Intel486 DX2 Microprocessor: Speed-Doubler Technology", Intel Corporation, Microcomputer Solutions, May/June 1992, page 2-5</ref>  The 66-MHz Intel486 DX2 were available for USD $682 each in 1,000-piece quantities.<ref>Intel Corporation, "New Product Focus: OEM: Speed-Doubling Technology Powers Intel486 DX2 66-MHz CPU", Microcomputer Solution, November/December 1992, Page 18</ref>

<gallery>
File:Intel 80486DX2 top.jpg|An Intel i486DX2-66 Microprocessor, top view.
File:Intel 80486DX2 bottom.jpg|The bottom view with gold plated pins visible.
File:KL Intel i486DX2 PQFP.jpg|Embedded i486DX2 (SL enhanced, [[Quad Flat Package|SQFP]] version).
</gallery>