[OpenBIOS] Why protected mode?

Andrew Kohlsmith akohlsmith at benshaw.com
Thu Jul 15 09:39:45 CEST 1999

> > That was only on the '286, which required a processor reset to get back
> > into real mode and was assisted by the keyboard controller, one of the
> > Great PC Hacks.  It is not as traumatic with '386 and beyond.

I also wanted to add that all this nonsense was necessary because int he
design of the 80286 there was a method of ENTERing protected mode, but no
clean way to get back.  I'm curious to know whether the double/triple fault
was used as a way back because that's how Intel had *designed* it, or if the
lack of method to come back to Real mode was an oversight.

Looking at pages like x86.org, I tend to think the latter.

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