ATI Technologies RADEON 7000 - Manual (Page 11)

7
Monitor Attributes Tab
The Attributes tab provides display data channel
(DDC) information.
DDC is the technology whereby the monitor
communicates to the graphics card all the resolutions
and refresh rates it supports. The RADEON™ family
of graphics cards are all DDC compliant.
By unchecking Use DDC information, you can
manually select the maximum resolution and refresh
rate of your monitor. However, this is only
recommended for older or non DDC compliant
monitors.