Old MS-DOS & WIN Software

Gil Carrick gilcarrick at comcast.net
Wed Dec 7 10:11:52 CST 2005


...
> >Is XP guaranteed to map 0x000c0000 physical  into c000:0 
> virtual in a 
> >VM86 session?  Does it keep the whole ROM space mapped to 
> its corresponding
> >physical addresses?  It certainly has to hide the video 
> RAM...   I would
> >have expected it to replace the ROM with one of its own as well.
> 
> I don't believe XP does anything more than copy the ROM into 
> a bank of RAM and then map the RAM.  

On Pentium systems, at least the current ones, a larger "page" is used to
map most of the kernel memory into every logical address space with a single
entry. IIRC the default mapping is 4 MB. 

Gil

> 
> Cheers,
> Chuck




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