BIOS & Pmode 
Author Message
 BIOS & Pmode

What is the best way to access a BIOS memory location from 32 bit protected
mode (DPMI)?
Right now I'm switching from 32 bit pmode to 16 bit real mode, reading the
necessary locations and returning to pmode.  This seems wasteful.  Is there
a formula to convert a 16 bit seg:off address to a 32 bit pmode address for
direct access or do I need to create a descriptor with its base at 40h.  I
appreciate any accurate info.
Thanks
Beanpole



Wed, 11 Dec 2002 03:00:00 GMT  
 BIOS & Pmode
As long as your protected mode segment starts at zero you can access the BIOS
data at
400h (*16 the real mode segment value + your offset), chances are though that
you have to create a new descriptor.

Cyrus W.

Quote:

> What is the best way to access a BIOS memory location from 32 bit protected
> mode (DPMI)?
> Right now I'm switching from 32 bit pmode to 16 bit real mode, reading the
> necessary locations and returning to pmode.  This seems wasteful.  Is there
> a formula to convert a 16 bit seg:off address to a 32 bit pmode address for
> direct access or do I need to create a descriptor with its base at 40h.  I
> appreciate any accurate info.
> Thanks
> Beanpole



Wed, 11 Dec 2002 03:00:00 GMT  
 BIOS & Pmode
Why don't you request DPMI host for a descriptor/selector for 1st megabyte
of RAM?

Btw, DJGPP (32-bit free GNU C/C++ compiler for DOS) has very good libraries
(DPMI, GO32, MOVEDATA, ...) for all the DPMI things you may ever need.

Why not to use standard solutions?

bye.
Alexei A. Frounze
-----------------------------------------
Homepage: http://alexfru.chat.ru
Mirror:   http://members.xoom.com/alexfru
PMode...: http://welcome.to/pmode

----------

Quote:

> ?e??? ?a???: alt.lang.asm; borland.public.tasm; comp.lang.asm.x86
> ?: BIOS & Pmode
> ?: 24 t? 2000 ?. 23:01

> What is the best way to access a BIOS memory location from 32 bit
protected
> mode (DPMI)?
> Right now I'm switching from 32 bit pmode to 16 bit real mode, reading
the
> necessary locations and returning to pmode.  This seems wasteful.  Is
there
> a formula to convert a 16 bit seg:off address to a 32 bit pmode address
for
> direct access or do I need to create a descriptor with its base at 40h.
I
> appreciate any accurate info.
> Thanks
> Beanpole



Wed, 11 Dec 2002 03:00:00 GMT  
 
 [ 3 post ] 

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