Message-ID: <F554E1189472D21198D000805F654BFE59FFCD@ntxchangerend.engr.rendition.com>
From: yjtseng <yjtseng AT micron DOT com>
To: "Salvador Eduardo Tropea (SET)" <salvador AT inti DOT gov DOT ar>, dj AT delorie DOT com,
        djgpp AT delorie DOT com
Cc: yjtseng AT micron DOT com
Subject: cwsdpr0.exe 4/14/99
Date: Wed, 14 Apr 1999 15:57:46 -0600
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Reply-To: djgpp AT delorie DOT com

All right,

Now, fact:	CR0=0x80000019 which means paging is on. If I maps physical
address 0xfb000000 to linear address using
__dpmi_physical_address_mapping(&mi) as shown in FAQ 18.7, the returned
linear address is 0xfb00000000 which the same as physical address
0xfb000000. How can this be? It does not make sense, right? Unless the
paging mechanism is off, which is not true, as evidenced by CR0=0x80000019.
Since paging is used, shouldn't the linear address be different from the
physical address after Int 31H, function 0800H?

Any idea? 

Thanks.

Jay

	-----Original Message-----
	From:	Salvador Eduardo Tropea (SET) [SMTP:salvador AT inti DOT gov DOT ar]
	Sent:	April 13, 1999 8:40 AM
	To:	yjtseng
	Subject:	Re: FW: cwsdpr0.exe 4/13/99

	Hi Jay:
		> What will happen if virtual memory is disabled (as is in
cwsdpr0.exe),
		> paging is enabled (as shown in CR0 I read), and pages need
to be swapped
		> out? 

	All the pages are marked as non-swap.
		> Is this a legitimate scenario? 

	Of course! as I told you DOS's EMM386 uses it to emulate EMS. The
code enters in PM and creates a virtual machine for the RM programs. That's
why a lot of PM programs for DOS can't run when EMM386 is loaded. Remapping
pages EMM386 can emulate EMS (hardware paged memory used in 286 machines).
		> Or, can you do paging without swapping pages to/from disk
storage?

	Paging mechanism is not only for VM. You can remap memory and
protect pages, for it you don't need swap at all.
	SET
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<http://www.geocities.com/SiliconValley/Vista/6552/>  Salvador Eduardo
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