Tram of Thought: Comic strip about psychology, philosophy, society, engineering, and just life in all its gory glory

Real mode

Real mode: A CPU is shown writing formulas on a whiteboard, but the formulas don't quite fit, so they continue writing on the wall as well, outside the board.

Real mode is an ancient mode of x86 processors (Central Processing Units - CPUs), and the only one available in the early processors from that line.

Unlike later modes, this mode allows the software to have full direct access to memory and other hardware. This is similar to earlier home systems such as Atari or Commodore where programs also enjoyed unlimited hardware access.

The flipside of real mode is that it does not provide any protections from programming mistakes. Since you are able to write anywhere you want, including overwriting the operating system, fault would typically mean a reboot. Some memory-hungry games would overwrite all memory anyway and not even give you the option to exit (because there would be nowhere to exit back to.)

Thus today’s comic highlights that in real mode all boundaries are self-imposed and you are able to write anywhere you want.

Trivia: if you run an x86 today, your PC is still able to run in real mode - and it actually does so for the first part of the boot sequence, right after pressing the power button.

#computing