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TheIntel486 DX2,[1] rumored as80486DX2 (later rebadgedi486DX2), is aCPU produced byIntel that was first introduced in 1992. The i486DX2 was nearly identical to thei486DX, but it had additionalclock multiplier circuitry. It was the second CPUchip to useclock doubling, whereby the processor runs two internal logicclock cycles 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 MHz Intel486 DX2 CPU uses the800 nm process technology.[2] With the internal clock doubler CPU, it boosts overall system performance between 50 and 70 percent above the original Intel486 DX series.[3] 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.[4] The 66-MHz Intel486 DX2 version performed 54 (Dhrystone V1.1)MIPS.[5]
The i486DX2-66 was a very popular processor forvideo games enthusiasts in the early to mid-90s. Often coupled with 4 to 8MB of RAM and aVLB video card, this CPU was capable of playing virtually every game title available for years after its release, right up to the end of theMS-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 offloating point calculations and the need for fastercache and morememory bandwidth. Developers began to target theP5Pentium processor family almost exclusively withx86 assembly language optimizations which led to the usage of terms such asPentium compatible processor for software requirements. An i486DX2-50 version was also available, but because the bus speed was 25 MHz rather than 33 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 fasterL1 cache mode, called "write-back", that improves performance. The original P24 version offered only the slower "write-through" cache mode.AMD andCyrix 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.[6] The 66-MHz Intel486 DX2 were available for USD $682 each in 1,000-piece quantities.[7]
Intel Datasheets
