386

The 386, formally known as the Intel 80386 and commonly referred to as the 386, is a 32-bit microprocessor released by Intel in 1985. It was the first member of the i386 family and marked a major shift in the x86 line by extending the architecture from 16-bit to 32-bit computing while remaining compatible with older software through real mode operation.

Key features include a full 32-bit instruction set, 32-bit registers, and 32-bit addressing. The processor introduced protected mode with hardware memory protection, paging, and support for virtual memory and multitasking. This enabled modern operating systems to implement isolated processes and memory management, laying the groundwork for 32-bit desktop and server software. The 386 generally required a floating-point unit for efficient floating-point math, with the optional 387 coprocessor commonly used in systems that needed high-precision arithmetic.

Two main variants exist: the 80386DX, which has a 32-bit data bus and 32-bit address space (up to 4 GB), and the 80386SX, introduced later, which uses a 16-bit data bus and a 24-bit address space (up to 16 MB). The SX was designed to be cheaper and was widely used in cost-sensitive systems, while the DX targeted higher performance machines.

Impact and legacy: the 386 enabled true 32-bit operating environments on the PC, facilitating early Windows versions with protected mode, as well as OS/2 and many Unix-like systems. It remained in production through the late 1980s and early 1990s and influenced subsequent generations of x86 processors, including the 486 and later Pentium line, helping to establish the modern PC architecture.

---