Notes on the Intel 8086 processor's arithmetic-logic unit

In 1978, Intel introduced the 8086 processor, a revolutionary chip that led to the modern x86 architecture. Unlike modern 64-bit processors, however, the 8086 is a 16-bit chip. Its arithmetic/logic unit (ALU) operates on 16-bit values, performing arithmetic operations such as addition and subtraction, as well as logic operations including bitwise AND, OR, and XOR. The 8086's ALU is a complicated part of the chip, performing 28 operations in total.1 In this post, I discuss the circuitry that cont...