How do I enable 16 bit mode on 32x86 processor

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Hi, I am working on a small hobby OS (with nasm assembler and c++).
I already have programmed some text on the screen and I have made some other small things.
I basicly want to switch the processor to 16 bit(real) mode to access some bios interrupts.
I already have read some on this site link
but I still dont quite understand how to do the switch.

What I have tried:

I've read a lot of books
I've browsed the web(but no success)
I've read intel manual(little bit unclear)

Posted 18-Feb-21 7:14am

MrProgrammer12

Updated 18-Feb-21 8:04am

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Dave Kreskowiak · Accepted Answer · 2021-02-18T08:04:00

Solution 1

As far as I know, todays processors, at least Intel's, start up in Real Mode at power on. Once out of Real Mode, there was no way to switch the processor back to Real Mode without resetting the processor.

Posted 18-Feb-21 8:04am

Dave Kreskowiak

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merano99 19-Feb-21 19:49pm

Every x86 Prozessor starts in Real-Mode. The use of BIOS-Interrups works and you dont need to switch. Why is ist nessarary to switch?
After switching to Protected Mode you can emulate the Real Mode by switching to Virtual 8086 Mode to access BIOS-Interrups. From Protected Mode you have to Reset the CPU to come back to Real-Mode.

Perhaps this is usefull:
https://stackoverflow.com/questions/59894016/switch-from-protected-mode-to-real-mode

Dave Kreskowiak 19-Feb-21 19:51pm

Perhaps you should be replying to the OP instead of me? That way, the OP gets a notification you posted something.

MrProgrammer12 20-Feb-21 12:50pm

thank you for the help guys, im gonna have a look at virtual 8086 mode.
:)