Leandro DUTRA wrote:
> 2008/3/23, Ian Manners <oice500@xxxxxxxxxx>:
>
> That was true of the 80186, but the 80286 was actually a protected
> mode processor. What killed it was DOS: OS/2 (and later MS Windows)
> needed it to run DOS real mode programs under virtual mode.
On a 286, protected mode and real mode are incompatible. Unlike a 386
the machine is in one state or the other. Getting to real mode from
protected mode or vice versa requires a complete reset of the processor.
OS/2 did run both real and protected mode programs at the same time
but it requires some fancy state save maneuvers after which you hold
your breath and reset the processor in order to change modes. Analagous
to pressing the reset button on the front of your PC every 30
milliseconds. It's the reason that Bill Gates was quoted as saying the
286 was a "brain dead" processor. I have to say that Intel hardware
engineers had no notions of how software guys might like to use the
hardware and never even conceived of rapid switching between modes for
software compatibility. Fortunately, my boss had some serious sessions
with Intel early in the 386 development cycle so the 386 was better than
it might have been. However, we never did convince them that the 386
ought to have hardware support for true virtualization.
> ...so you
> could use '/' instead of '\' for directory separation in path names as
> you do in POSIX. That was supposed to become the default in MS DOS 3
> as a step to Xenix, but in the way to v3 MS realise it needed the
> proprietary lock in and thus OS/2 was born.
>
Sorry, but the OS/2 guy who knows full well that OS/2 (contrary to
popular belief) is an IBM conceived and designed product says.... huh???
Chuck Norcutt
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