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Old 11-04-07, 09:24 AM   #7
pe1chl
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Join Date: Aug 2003
Posts: 1,026
Default Re: Request for new Sticky about resolution issue!

The reason it works at analog is because analog output has the potential to output much larger pixel rates.
With analog output, each pixel is output as 3 analog values of 8 bits each (0-255), the card can do that at about 350 MHz.
For digital output, the 3 8-bit values for each pixel are output serially. So even with a much larger serial clock value, the card actually can output only about 135 MHz at pixel level (which is 24 times more at bit level).

The maximum bitrate is a "soft" limit. Your card's specs may say the maximum is 135 MHz but your actual card's performance could be a bit better than that.
So turning off the checking can make it working while the guaranteed performance of the card would not allow it.

Newer cards are guaranteed to work up to 155 MHz for single link DVI.
To solve the problems for larger resolutions, some cards have dual link DVI which means it can output two pixels at the same time over two different connections, effectively doubling the pixel rate.
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