Darren New wrote:
> Invisible wrote:
>> So when you say "works on any reasonably modern PC", what you 
>> *actually* mean is "works on any brand new bleeding-edge PC"?
> 
> No. I believe it was the 386 that added the capability.
> 
> You know, two generations back before the Pentium came out?
> 
> Added primarily to emulate multiple "DOS boxes" under Windows.

The 386 or so added "virtual mode" (or whatever the exact term is) that 
makes the CPU act as if it's in real mode, but it's really in protected 
mode, and the OS can control the page mappings and so forth.

You can use that to make real mode applications (e.g., DOS programs) 
think they have the machine to themselves. But that doesn't work for a 
protected mode program such as an OS.

-- 
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