i486SX

The i486SX, often stylized as 486SX, was a lower-cost variant of Intel's i486DX microprocessor. Released in June 1991, it was designed to be a more affordable option for personal computers, aiming to bridge the gap between the i386SX and the full i486DX.

The primary difference between the i486SX and its i486DX sibling was the disabling of the floating-point unit (FPU). This meant that while the i486SX possessed the same core integer processing capabilities and features like an on-chip cache and pipelined architecture as the i486DX, it could not perform floating-point calculations directly. For applications that heavily relied on floating-point math, such as CAD or scientific software, users would often have to purchase a separate coprocessor, the i387SX, to achieve comparable performance.

Another distinction was that early i486SX processors were often manufactured using i486DX chips that had a defective FPU. Intel would then disable the FPU before shipping them as i486SX. This practice was phased out as production of dedicated i486SX dies matured.

The i486SX was available in clock speeds ranging from 16 MHz to 33 MHz. It featured a 32-bit external data bus and a 32-bit address bus, supporting up to 4 GB of RAM. Despite the lack of an integrated FPU, the i486SX offered a significant performance improvement over previous generation processors like the i386 and was a popular choice for mainstream desktop computers throughout the early to mid-1990s. Its existence helped make the 486 architecture more accessible to a wider market.