Date: Wed, 26 Sep 2001 15:01:17 +0200 (CEST)
From: Kovacs Viktor Peter <vps AT winnie DOT obuda DOT kando DOT hu>
To: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
cc: <djgpp AT delorie DOT com>
Subject: Re: Run djgpp program in real dos got SIGSEGV signal ?
In-Reply-To: <3791-Wed26Sep2001130017+0300-eliz@is.elta.co.il>
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[On Wed, 26 Sep 2001, Eli Zaretskii wrote:]
> > From: Kovacs Viktor Peter <vps AT winnie DOT obuda DOT kando DOT hu>
> > Newsgroups: comp.os.msdos.djgpp
> > Date: Wed, 26 Sep 2001 11:26:27 +0200
> >  Under the windows dpmi all segments have a limit of 4Gb. Dos based
> >  dpmi servers limit the segments to the allocated ram.
> That's not true: at least with CWSDPMI and other DOS DPMI servers, the
> data segment can be much larger than the installed RAM.

 It can be, but you have to set it expicitly... (by enabling near pointer
 support), so you can use 'negative' offsets to access memory before the
 data segment's base address.

> The Windows DPMI host, on the other hand, is, indeed, known to limit
> the available DPMI memory to the installed RAM or to 64MB, whichever
> is larger.

 Yes, the allocatable memory can be limited, but windows uses a page based
 protection and virtualizes the low memory. This is why you don't have
 to use any segment based protection.

   Viktor

ps:
 Check the segment descriptor dump on your dos screen, and compare them
 with the windows version. (divide with zero, to get the same error
 screen)