INT 2F, subfunc 13h

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2 total messages Started by cs106132 Sun, 26 May 1991 06:45

#1222

Author: cs106132
Date: Sun, 26 May 1991 06:45

19 lines
1153 bytes

   Hi,
I found out that Int 2F, subfunc 13h is used to set the Int 13h address
and get the original one from DOS.  If I get it right, DOS device driver
grabs the original ROM address and replaces it with its own handler.  But
there is a way to find it out using undocumented Int 2F, 13h.  Something
like this:
 
   DS:DX points to current handler to set
   AX = 13h
   Int 2F
   DS:DX now contains the original address
   store away DS:DX
   Int 2F again to set it back to what it was

Does anyone have an idea what this is all about?  Any pointers will be
appreciated.

Ted Lee

Re: INT 2F, subfunc 13h

#1223

Author: Brad J. Caster
Date: Mon, 27 May 1991 02:44

15 lines
886 bytes

In article <1991May26.064558.13108@umbc3.umbc.edu> cs106132@umbc5.umbc.edu (cs106132) writes:
...
>   DS:DX points to current handler to set
>   AX = 13h
    ^^^^^^^^   AH = 13h  or AX = 13xxh
>   Int 2F
>   DS:DX now contains the original address
>   store away DS:DX
>   Int 2F again to set it back to what it was
...




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