80286 Protected Mode Test

Noel Chiappa jnc at mercury.lcs.mit.edu
Sun Mar 7 08:40:30 CST 2021

    > From: Jim Stephens

    > The 286 can exit protected mode with the LOADALL instruction.

Really? So why all the hullabaloo about Triple Faults:


back in the day; and why did IBM set up the keyboard controller so it could
send a RESET signal (so people could get out of protected mode)? Or is it
that LOADALL (which was also undocumented early on, so maybe that's why the
IBM thing) could be used to cause a triple fault?


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