i486DX4

The i486DX4 is a 32-bit microprocessor in Intel's 80486 family. It was introduced in the mid-1990s as a higher-clocked member of the DX line and is notable for incorporating a fourfold internal clock multiplier. This design allowed the processor to reach speeds around 100–133 MHz from lower external clock sources such as 25, 30, or 33 MHz. The “DX” designation indicates the presence of an integrated floating-point unit (FPU).

Compared with earlier 486 models, the i486DX4 emphasized higher core frequencies while maintaining compatibility with the 80486 instruction set and protected-mode operation. It typically included the on-die cache characteristics associated with the generation and retained the 32-bit architecture and general purpose registers of the 486 family.

Packaging and compatibility: The DX4 variants were commonly implemented in Socket 3/PGA form factors appropriate for 486-class desktop systems. External clock inputs varied, with 25, 30, or 33 MHz buses yielding core speeds of roughly 100, 120, or 132–133 MHz, depending on the model. Production used process technology typical of mid-1990s x86 CPUs.

Variants and speeds: The main speed grades were i486DX4-100, i486DX4-120, and i486DX4-133 (often marketed as 132 MHz in practice). These speeds reflect different external clock sources, all multiplied by four to reach the indicated core frequency.

Impact and legacy: The i486DX4 represents the apex of the 486 era in terms of clock speed and multiplier technology. It preceded Intel’s Pentium line, which began to dominate the market in 1995–1996, and remained in use in budget and enterprise systems for several years as software and operating systems evolved.