Q40573: Problems with Using the Digital Output of a VGA Adapter

Article: Q40573
Product(s): See article
Version(s): 5.00 5.10
Operating System(s): MS-DOS
Keyword(s): ENDUSER | S_QUICKC | mspl13_c
Last Modified: 16-MAY-1989

Problem:

When I run programs, such as GRDEMO, that call the graphics function
_setvideomode, a border is displayed around my monitor. Also, the
functions _remappalette and _remapallpalette do not seem to work
correctly.

Response:

Some VGA display adapters have analog- and digital-output
capabilities. The above behavior occurs when the digital output of a
VGA display adapter is connected to the monitor.

When the digital output is connected to an ECD (EGA monitor), a green
border is observed. When the digital output is connected to a
multisync class monitor, a gray border is observed. In either case,
remapping the palette does not function. When the analog output is
connected to a multisync or VGA monitor, the correct behavior is
observed.

The problem is that the graphics adapter is rightfully determined to
be VGA class -- although for practical purposes it is really EGA
class. At this point, the C graphics library treats the display
incorrectly as VGA. Connecting a digital monitor to the digital output
of a VGA adapter is a non-standard hardware configuration (the digital
output of a VGA graphics adapter is non-standard). The behavior of a
non-standard hardware configuration is unpredictable.

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