Editing Intel 8086 (section)

===Buses and operation===
All internal registers, as well as internal and external data buses, are 16&nbsp;bits wide, which firmly established the "16-bit microprocessor" identity of the 8086. A 20-bit external address bus provides a 1&nbsp;[[Mebibyte|MiB]] physical address space (2<sup>20</sup> = 1,048,576 x 1 [[byte]]). This address space is addressed by means of internal memory "segmentation". The data bus is [[multiplexed]] with the address bus in order to fit all of the control lines into a standard 40-pin [[dual in-line package]]. It provides a 16-bit I/O address bus, supporting 64&nbsp;[[Kilobyte|KB]] of separate I/O space. The maximum linear address space is limited to 64&nbsp;KB, simply because internal address/index registers are only 16&nbsp;bits wide. Programming over 64&nbsp;KB memory boundaries involves adjusting the segment registers (see below); this difficulty existed until the [[80386]] architecture introduced wider (32-bit) registers (the memory management hardware in the [[80286]] did not help in this regard, as its registers are still only 16 bits wide).