Real mode

Real mode is an operating mode that enables the Intel 286 and newer processors to take on the attributes of the lower 8086 or 8088 processors, allowing them to run older programs. Real mode offers a higher clock speed, but limits the processor to only use 16-bit instructions and a minimum of 1 MB of RAM (random-access memory). For example, legacy MS-DOS operating systems run programs in real mode.

A20, CPU terms, EMS, Operating system, Protected mode, Virtual real mode