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From:	"A. Wik (awik32 AT gmail DOT com) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
Date:	Mon, 26 Feb 2024 13:30:13 +0000
Message-ID:	<CALPW7mRUipL8RhJLWMo+8LOzqGhL83ZnrQe10Rz8tizEt_pt9w@mail.gmail.com>
Subject:	Re: DJGPP documentation updates
To:	djgpp AT delorie DOT com
Reply-To:	djgpp AT delorie DOT com

On Mon, 26 Feb 2024 at 12:56, Eli Zaretskii (eliz AT gnu DOT org) [via
djgpp AT delorie DOT com] <djgpp AT delorie DOT com> wrote:
>
> > From: "A. Wik (awik32 AT gmail DOT com) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
> > Date: Mon, 26 Feb 2024 08:23:27 +0000
> >
> > > I think there's a misunderstanding here.  The issue at hand is whether
> > > the DOS memory's linear address, as it appears within a certain VM,
> > > can ever have the value above 1MB.  If the linear address is _always_
> > > below 1MB, then for all practical purposes it is the same as the
> > > "physical address", since what the VM does under the hood is none of
> > > the business of the DJGPP programmer.
> >
> > Linear V86 addresses are obviously below 1 MB, but (via the page
> > tables) they can be (and in Wndows often are) mapped to any physical
> > address, including above 1 MB.
>
> Of course.  But the misunderstanding I was pointing out is exactly
> this: a programmer doesn't care about those page tables in this case,
> because DOS memory is by definition "physical".
>
> We basically agree about the facts, but not about their impact on the
> documentation that is the subject of this thread.

Perhaps you mean that the distinction doesn't matter, because the
addresses are always mapped in while the VM is running?  But the
distinction does matter if you're going to pass the address to a
hardware device.  It can also matter if you're going to do certain
things with paging, such as turning it on or off or in some cases,
when you're manipulating the page tables.

-Albert.

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