486

The 486, formally the Intel 80486, is a family of 32-bit microprocessors introduced by Intel in 1989 as the successor to the 80386. It represented a significant architectural advance for personal computers, combining an enhanced instruction set with on-chip cache and improved performance through internal pipelining. The 80486 maintained compatibility with the 386 instruction set and system interfaces, enabling straightforward upgrades for existing software and hardware.

A defining feature of the 486 is its on-chip cache and integrated floating-point unit in the DX variants. The CPU includes an 8 KB on-chip cache (split into 4 KB for data and 4 KB for instructions) and a five-stage instruction pipeline. The 486 also supported paging and virtual memory, continuing the x86 era’s emphasis on software portability and memory management. The 486SX variant lacked the floating-point unit, offering a lower-cost option with reduced performance for floating-point tasks.

Variants and clock speeds evolved through the 1990s. The original 486DX operated around 20–33 MHz, with the 486SX offered at lower configurations. Later, clock-doubling versions such as the 486DX2 and internal-multiplier versions like the 486DX4 increased practical speeds, commonly reaching 66–100 MHz and beyond. The 486 family used a 32-bit data and address bus, enabling access to up to 4 GB of memory, and ultimately laid the groundwork for more advanced processors in the Pentium line.

Impact and legacy are marked by substantial performance gains over the preceding 386, particularly for compute-heavy and graphical tasks. The 486 remained a mainstay in desktop PCs through the mid-1990s and contributed to the rapid evolution of operating systems and software. Its introduction helped define the transition from simple, bus-oriented CPUs to more integrated, high-performance microprocessors in personal computing.