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From: schuster@dasys1.UUCP (Michael Schuster)
Newsgroups: alt.msdos.programmer,comp.sys.ibm.pc,comp.binaries.ibm.pc.d
Subject: Re: Patch GRAPHICS.COM (DOS 4.0) to run under DOS 3.3 ?
Message-ID: <11234@dasys1.UUCP>
Date: 15 Nov 89 23:14:59 GMT
References: <2961@einstein.ptolemy.arc.nasa.gov>
Reply-To: schuster@dasys1.UUCP (Michael Schuster)
Organization: The Big Electric Cat; New York, N.Y. USA
Lines: 29

In article <2961@einstein.ptolemy.arc.nasa.gov> raymond@ptolemy.arc.nasa.gov (Eric A. Raymond) writes:
>For obscure reasons, I need to run GRAPHICS.COM under DOS 3.3 (to get
>VGA screen dumps).  Unfortunately it gives me the message:
> 
>    Incorrect DOS Version
>
>when I run it under DOS 3.3. I just tried tracing through the binary,
>made one obvious change, one less obvious change, but it still would't
>work.
>
>Any patches out there?


The version-check code in most of the DOS 4 external programs looks
like this:

B4 30		MOV AH,30
CD 91   	INT 21
3D 04 00	CMP AX,4
75 03		JNZ 176B

If you replace the last line of code (75 03) with NOP's the version test
will be ignored.


-- 
l\  /l'   _  Mike Schuster          ...!dasys1!schuster
l \/ lll/(_  Big Electric Cat       schuster@dasys1.UUCP   CIS:70346,1745
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