Message-ID: <19990925165811.11399.rocketmail@web1406.mail.yahoo.com>
Date: Sat, 25 Sep 1999 09:58:11 -0700 (PDT)
From: Prashant TR <prashant_news AT yahoo DOT com>
Subject: Re: Protected Mode problem (note: Eli Zaretskii)
To: djgpp AT delorie DOT com
Cc: nicolas DOT gasnier AT wanadoo DOT fr
MIME-Version: 1.0
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Reply-To: djgpp AT delorie DOT com



--- Nicolas Gasnier <nicolas DOT gasnier AT wanadoo DOT fr>
wrote:
> I think that you don't need to take care about
> the A20 line and whatever when you spawn a program.
...
...
> A few solutions :
> - run your program in full dos mode without any
> memory managers (emm, qemm, himem...) and don't
> spawn it from your DJGPP program.
> - rewrite your program using DPMI interface

The program I'm trying to spawn is a 16-bit real mode
program, not a program written with DJGPP. I'm already
in MSDOS mode (I have to be if I need to access the
GDT, etc) and there are no memory managers.

Why I want to do is because I'm trying to get direct
access to the extended memory (which may be any
portion of extended memory; not just the portion of my
DS). If I did that in DJGPP, my program would crash
with a SIGSEGV. But I don't think merely accessing
registers like CR0, etc. should affect anything as
long as I set them back to what they were. I even
disable interrupts to make sure the control never goes
to the DPMI.

It seems that CWSDPMI reprograms the PICs to
accomodate IRQ0-7 starting at INT 78-7fh. I'm not sure
about this and I need clarification.

Thanks for the help. But can you please help me some
more ?

> >  When I spawn a real mode program that itself
> >switches to protected mode and does some extended
> >memory access, I get a severe problem and my
> original
> >parent DJGPP program crashes.
> >
> >  I've set everything back to normal including A20
> >line, GDT, IDT, TS flag and almost everything you
> can
> >think of. And what are the hardware interrupts
> DJGPP
> >uses for IRQ0-7. Is it INT 78-7fh ? The Task
> register
> >is modified my my program. I can't of course set
> this
> >back to what it was.
> >
> > So, what could be the problem.
> >
> >And does DJGPP allow me to make reference to any
> >portion of the extended memory ? I don't think it
> >does.
> >Someone please help.
> >
> >Thanks,
> >Prashant TR

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