80286 Protected Mode Test

[Guy Sotomayor]

On 3/15/21 7:23 AM, Noel Chiappa via cctalk wrote:
>      > From: Guy Sotomayor
>
>      > the LOADALL instructions including all of it's warts (and its inability
>      > to switch back from protected mode)
>
> Good to have that confirmed (for the 286; apparently it works in the 386).
The 386 loadall instruction was different (not really a surprise since 
the internal microarchitecture was different).  The 386 didn't need to 
do this "hack" because it had vm86 mode for tasks so that accomplished 
what everyone was really using LOADALL on the 286 for.
>
>      > the other way to get back to real mode from protected mode is via a
>      > triple-fault.
>
> Any insight into why IBM didn't use that, but went with the (allegedly slow)
> keyboard hack?
At this point I don't recall.  But I suspect it was allegedly simpler 
conceptually.

-- 
TTFN - Guy