🚀 go-pugleaf

 
 Sorry if this has been asked before, but I haven't been reading this
group for long.


 In 386 enhanced mode, windows 3 implements virtual memory using
hardware paging. However, when attempting to run a non-windows
application it seems to require enough contiguous physical memory for
the application to run. Also the delays and disk accesses that can
occur when switching between non-windows applications seems to
indicate that the whole Virtual 8086 VM is swapped as one unit,
either all in RAM or all swappped out.

 So, is there any reason why windows doesn't page non-windows
applications? I have read the Intel 80386 manuals and can see nothing
that would indicate that a V8086 VM can't use paging. The way that I
understand that it would work would be that if the Real Mode
application (in the V8086 VM) attempts to access a memory location
that is not present in RAM, a page fault exception is generated,
which is serviced by the Protected mode code in the same way as a
page fault occuring in a protected mode (ie windows) application. The
page is then brought into memory and following the IRET from the
exception handler, the Real mode application continues as if nothing
had happened. As I understand it, the one thing that must never be
paged is the page fault exception handler.

 Have I misunderstood the way that paging and page faults are handled
in Virtual 8086 mode? If I haven't misunderstood it, then is there
some other reason why Windows cannot allow a non-windows application
to be paged? 


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Graham Murray			  Email gmurray@ibmpcug.co.uk
Senior Programmer		    OR  gmurray@cix.compulink.co.uk
Gravatom Technology Ltd		  Voice +44 329 823986
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