From:	"Chunfeng Zhao" <chunfengzhao AT hotmail DOT com>
Newsgroups:	comp.os.msdos.djgpp
References:	<Pine DOT LNX DOT 4 DOT 33 DOT 0109261454350 DOT 9725-100000 AT winnie DOT obuda DOT kando DOT hu>
Subject:	Re: Run djgpp program in real dos got SIGSEGV signal ?
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Date:	Wed, 26 Sep 2001 09:55:45 -0700
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp
Reply-To:	djgpp AT delorie DOT com

Thanks a lot!
I am using the code from DJGPP V2 QuickGraphic programming Guide,  in the
VBE2.0 section, I copied the Farptr part of the sample code. The program
give Page fault when use movedata() to transfer data from system memory to
graphic frame buffer.

Where Can I find some sample code that include the full implementation for
programming the graphic card directly ?
Thanks again ?

Chunfeng Zhao
"Kovacs Viktor Peter" <vps AT winnie DOT obuda DOT kando DOT hu> wrote in message
news:Pine DOT LNX DOT 4 DOT 33 DOT 0109261454350 DOT 9725-100000 AT winnie DOT obuda DOT kando DOT hu...
> [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)
>
>

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