Computer Related > PC monitor detection Computing Issues
Thread Author: Focusless Replies: 2
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New Tue 7 Feb 12 09:41 
 PC monitor detection - Focusless
When possible I use my work laptop in (Windows XP) extended desktop mode - in the office that's with a 17" 4:3 monitor which has a resolution 1280x1024. At home I use a 19" 16:9 TV with a resolution of 1360x768.

The laptop only has a VGA connection, yet it sets the extended desktop resolution as appropriate depending on which monitor is connected. I would expect that with a digital connection (eg. DVI, HDMI) but I was surprised it can do that with VGA.

In simple terms, how does it do it?
Last edited by: Focus on Tue 7 Feb 12 at 09:41
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New Tue 7 Feb 12 10:11 
 PC monitor detection - Zero
Its called DDC - Display Data Channel. Its a means of the monitor telling the video card its cababilites resolution wise.

It used to be just grounding a combination of 4 pins to provide a binary code to the card, but then the standard morphed into a serial data connection over the unused pins.


So in effect the monitor says to the video card I can be driven be driven in XXX resolutions.

Its been a feature of analogue PC monitors for absolute ages.
Last edited by: Zero on Tue 7 Feb 12 at 10:12
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New Tue 7 Feb 12 10:13 
 PC monitor detection - Focusless
Right - so it is a digital protocol, over the analogue interface. Interesting - thanks.
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