Prior to the Intel 8086 processor (and the IBM PC, which
ensured its popularity), Intel produced a microprocessor called
the 8080 which formed the basis for a common generic
microcomputer Operating System, CP/M. This processor had a
16-bit address bus and thus supported a maximum of 64K (bytes)
of memory.
The 8080's 16-bit address was a "real" address; that is, no
conversion was required to transform the 16-bit address value
into a "real" or physical memory byte-cell address.