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From: Brian Inglis <Brian DOT Inglis AT SystematicSW DOT Invalid>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Strange VESA problem
Organization: Systematic Software
Message-ID: <gi3el01sded5u6qe9dpk2vq8lc4hmmg92t@4ax.com>
References: <20040926034158 DOT 24216 DOT 00001082 AT mb-m10 DOT aol DOT com>
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Date: Sun, 26 Sep 2004 18:58:59 GMT
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To: djgpp AT delorie DOT com
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On 26 Sep 2004 07:41:58 GMT in comp.os.msdos.djgpp, jbs30000 AT aol DOT com
(JBS30000) wrote:

>I have a dual boot computer, I can either boot into Windows XP or DOS from
>Windows 98 ( from http://newdos.yginfo.net/msdos71/index.htm).
>Anyway, I'm messing around geting VBE info with function 0 and then printing it
>out on the screen, and, under the DOS box from Windows XP, everything runs
>fine, but try to run my program under pure DOS and none of the strings return
>anything.
>I called my VBE info block structure "vesainfo".  For an exaple, using long
>OEM_String_PTR I'll show how I get the string to print.

It would help if you posted all the relevant parts of the real code. 

>I have variables char OEM_String[255]; and short Real_Mode_PTR;
                                            ^^^^^
Real_Mode_PTR needs to be at least 20 bits: use unsigned int or long. 

>To get the OEM String pointer:
>Real_Mode_PTR = ((vesainfo.OEM_String_PTR >> 16)  << 4) +
>(vesainfo.OEM_String_PTR & 0xFFFF);
>        dosmemget(Real_Mode_PTR & 0xFFFF, 255, &OEM_String);
                                 ^^^^^^^^
The pointer's likely to be an address over 0xA0000, so this won't
help, add another digit: 0xFFFFF and use in the previous statement, or
mask the high half with 0xFFFF in the previous statement: 
Real_Mode_PTR = (((vesainfo.OEM_String_PTR >> 16) & 0xFFFF)  << 4)
			+ (vesainfo.OEM_String_PTR & 0xFFFF);

OR

Real_Mode_PTR = (((vesainfo.OEM_String_PTR >> 16) << 4)
		+ (vesainfo.OEM_String_PTR & 0xFFFF)) & 0xFFFFF;

>Now, if I 
>printf("Chipset or OEM              %s \n", &OEM_String);
>under Windows XP DOS box, it prints out the string, but under pure DOS, it
>doesn't.  Does anybody have any ideas why?  Thanks.

-- 
Thanks. Take care, Brian Inglis 	Calgary, Alberta, Canada

Brian DOT Inglis AT CSi DOT com 	(Brian[dot]Inglis{at}SystematicSW[dot]ab[dot]ca)
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