DDC?

RAZOR0018 · November 13th, 2007, 12:29 AM

What is DDC and what should it be set as when disabled in control panel? I had to do this in order to stop the desktop refresh every log on after restart with ati 6.7+cp installed. I also found this while googling:

I’m experiencing the 60Hz refresh rate bug after installing the drivers...
In Windows 2k/XP, ALWAYS disable DDC in the ATI "Displays/Monitor" CP after installing drivers to be able to use ALL the refresh rates and resolutions your monitor supports.

Mac Daddy · November 13th, 2007, 12:49 AM

First off welcome to NGOHQ.com

Some info for you hope it helps google here too

Quote:

Option DDCMode boolean If set to false, (the default), then XFree86 will not attempt to query the monitor to discover the various video modes it supports. Rather, for each screen resolution (mode) defined in XF86Config (5x), XFree86 will pick the best matching Video Electronics Standards Association (VESA) standard mode timing which the monitor is capable of (according to its HorizSync
and VertRefresh
settings in XF86Config(5x). (XFree86 has a built-in list of all VESA standard mode timings.)

If set to true,
then instead of relying VESA standard mode timings, XFree86 will attempt to query the monitor using the VESA Display Data Channel Command Interface (DDC/CI) standard. If the display device can be successfully queried, then XFree86 will read the list of mode timings which the monitor claims to support. For each mode defined in XF86Config(5x), XFree86 will pick the best matching mode timing from the list of mode timings the monitor returns.
Note that not all monitors and not all Radeon cards support the VESA DDC/CI standard. If DDCMode
is enabled, but the monitor and/or card does not support the VESA DDC/CI standard, then XFree86 will emit a warning message and use the standard VESA mode timings instead.
The advantage of not using DDCMode
is that the VESA standard mode timings are supported by virtually all monitors. Additionally, a monitor which does not
support the VESA standard mode timings will almost certainly not support the VESA DDC/CI standard.

The advantage of using DDCMode
is that your particular monitor may support non-standard (i.e., non-VESA) mode timings which are better (e.g., a higher refresh rate) than the VESA standard mode timings. Additionally, for flat panel displays being used in analog mode, DDCMode
will avoid using unstable modes (some VESA standard modes don't really work with these panels).

Source:
Radeon Manual Page - MorLUG

Dyre Straits · November 13th, 2007, 02:22 AM

Quote:

Originally Posted by RAZOR0018

What is DDC and what should it be set as when disabled in control panel? I had to do this in order to stop the desktop refresh every log on after restart with ati 6.7+cp installed. I also found this while googling:

I’m experiencing the 60Hz refresh rate bug after installing the drivers...
In Windows 2k/XP, ALWAYS disable DDC in the ATI "Displays/Monitor" CP after installing drivers to be able to use ALL the refresh rates and resolutions your monitor supports.

The quote you found via Google is directly from the instructions included in the Omegadrivers.

DDC Enabled restricts the monitor from going into Resolutions and Refresh Rates that the installed drivers understand as being "out of range" for that particular monitor. If the video drivers don't recognize the display/monitor that's connected, the default resolution and refresh rate will be used.

So, the workaround for this limitation is to Disable DDC so that the otherwise "KNOWN" resolutions and refresh rates can be used. However, it CAN cause permanent damage to the display device if the ACTUAL limitations are exceeded.