Reverse-engineering the 8086 processor’s address and data pin circuits

The Intel 8086 microprocessor, released in 1978, is a revolutionary chip that started the x86 architecture. This blog post focuses on a specific aspect of the chip’s design: the address and data pins that connect it to external memory and I/O devices. Due to limitations in the number of pins available for functionality, Intel had to multiplex the address, data, and status roles of certain pins. This multiplexing, combined with the 8086’s 20-bit address space and 16-bit data bus, resulted in four distinct pin circuits. The post explores the complexity of the address and data pins and provides an overview of their functionality.

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