[OpenBIOS] Why protected mode?

Timothy J. Massey tmassey at iname.com
Thu Jul 15 16:25:26 CEST 1999

On Thu, 15 Jul 1999 15:03:45 -0400 (EDT), Kevin P Lawton wrote:

>Should have dropped real mode, had the CPU start
>out in protected mode, and today we'd all have
>protected mode only BIOSs.  Oh well, such is life.

And how would these computer have run DOS?  Or Windows?  The only OS
available before 1994 or so that didn't use real mode code was OS/2.  Did
everybody switch over to OS/2?  So how could Intel drop real mode?  In fact,
people's biggest complaint with OS/2 in the late 80's was OS/2 Compatibility
Box:  the way that it ran real-mode DOS programs.  If people weren't willing
to use an OS that allowed them to run a decent percentage of their old
software, why would they use a computer that allowed them to run *none* of
their old software!

Think about the difficulty that IBM caused for itself when they dropped ISA
in favor of MicroChannel.  The decision to go MicroChannel was made for
almost identical reasons that you would have wanted Intel to change designs
with the 286:  a better way of doing things.  I think the marketplace voted
on which way they wanted to go...

One other point to run this into the ground:  look at the success that Intel
has had so far in changing their architecture with IA-64.  We've been
waiting for, what?  3 years now?  And with what result?

In an environment as loose as the PC (as the author of Bochs I'm sure
knows), anything that isn't 100% backward compatible is horribly frowned
upon.  Companies like Apple can change CPU designs with success because they
control every detail of the hardware, OS and software.  In the PC world, we
aren't too open to that level of control.

Tim Massey

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