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#214 Reading VGA DAC Register returns erroneous result

0.63
closed
graphics (66)
5
2012-09-07
2005-02-11
JAL
No

When reading the VGA DAC Address Write Mode Register
(port 0x3c8), DOXbox returns 0xff instead of the
expected value. The following piece of code taken from
the Obitus game illustrates the problem:

mov dx,03C8
mov al,00
out dx,al
inc dx
mov al,00
out dx,al
mov al,00
out dx,al
mov al,00
out dx,al
mov dx,03C8
in al,dx

The last in should return 01 in al, as after three writes
the next DAC index is reached. However, DOSbox returns
0xff. I included a simple program that outputs 1 in the
NTVDM, but 255 (0xff) in DOSbox.

JAL

Discussion

  • JAL
    JAL
    2005-02-11

    Simple testprogram that shows the bug

     
    Attachments
  • Peter Veenstra
    Peter Veenstra
    2005-02-11

     
    Attachments
  • Peter Veenstra
    Peter Veenstra
    2005-02-11

    Logged In: YES
    user_id=535630

    added a patch that should do it.
    If you agree to it I will commit it.

     
  • JAL
    JAL
    2005-02-14

    Logged In: YES
    user_id=990442

    that seems to do the trick, can't test it here however.

     
  • Peter Veenstra
    Peter Veenstra
    2005-02-14

    Logged In: YES
    user_id=535630

    The bug has been fixed.
    Wait for the upcoming new version to see it.

    Or:

    The updated source is available by cvs.

    See the link on top of the screen for information on how to get
    the new sources.

    The DOSBox Team