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DJGPP EGA MEMORY ACCESS
http://forums.osdever.net/viewtopic.php?f=15&t=352
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Author:  smeezekitty [ Thu Apr 29, 2010 3:43 pm ]
Post subject:  DJGPP EGA MEMORY ACCESS

Ok, Ok, its not really OS dev but i thought you might be experienced in protected mode.
I am using an EGA mono card and the memory is at 0xA000:0000 but when i try to access it directly, it segmentation faults.
And if i try to access it with _fpokeb, the computer reboots for no reason.
It is a 486/33 with 12 megs of ram :mrgreen: .

Author:  Kieran [ Thu Apr 29, 2010 3:53 pm ]
Post subject:  Re: DJGPP EGA MEMORY ACCESS

Have you got a valid GDT?

Author:  smeezekitty [ Thu Apr 29, 2010 3:57 pm ]
Post subject:  Re: DJGPP EGA MEMORY ACCESS

GDT = Global descriptor table?
Protected mode is setup by a dpmi server so i assume so, but i am a noob in protected mode.

Author:  Kieran [ Thu Apr 29, 2010 4:01 pm ]
Post subject:  Re: DJGPP EGA MEMORY ACCESS

Hmm, i thought you were talking about code compiled in GJGPP, running on a bare pc.

Can you describe the environment?
OS?

Author:  smeezekitty [ Thu Apr 29, 2010 4:05 pm ]
Post subject:  Re: DJGPP EGA MEMORY ACCESS

Its MS-DOS 6.0.

Author:  Kieran [ Thu Apr 29, 2010 4:15 pm ]
Post subject:  Re: DJGPP EGA MEMORY ACCESS

Doesnt MSDOS have an EGA interface or driver???

Author:  smeezekitty [ Thu Apr 29, 2010 4:22 pm ]
Post subject:  Re: DJGPP EGA MEMORY ACCESS

I meant graphics mode ;)

Author:  Kieran [ Fri Apr 30, 2010 6:59 am ]
Post subject:  Re: DJGPP EGA MEMORY ACCESS

Yeah I know mate, im not sure if direct acces is allowd to that memory???

But i know there are EGA drivers that provide interrupt service for EGA displays...

Author:  smeezekitty [ Fri Apr 30, 2010 1:34 pm ]
Post subject:  Re: DJGPP EGA MEMORY ACCESS

Definitely possible:
http://www.allegro.cc/manual/api/direct ... eo-memory/

Author:  smeezekitty [ Sun May 02, 2010 12:25 am ]
Post subject:  Re: DJGPP EGA MEMORY ACCESS

Help?

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