on-board video cards [LWN.net]

on-board video cards

Posted Sep 29, 2007 21:49 UTC (Sat) by giraffedata (guest, #1954)
In reply to: on-board video cards by pm101
Parent article: What every programmer should know about memory, Part 1

It's not the physics, but the modernness that I think makes the refresh not necessary for LCDs at the level it is for CRTs: If I were designing a monitor in the 1990s out of parts that need to be refreshed (even a CRT), I would put required refresh function inside,rather than pass the responsibility off to the computer. In SVGA days, though, it probably made sense to keep the monitor dumb.

But I guess DVI designers decided the computer wants to update the picture by a full raster scan 60 times a second anyway, so there's no need for internal refresh. Doing a little reading just now, it looks like the DVI data stream is a simple raster scan. It even apparently has "blanking intervals," though they couldn't possibly be for same purpose as on a CRT.

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on-board video cards

Posted Sep 29, 2007 23:06 UTC (Sat) by foom (subscriber, #14868) [Link]

But I guess DVI designers decided the computer wants to update the picture by a full raster scan 60 times a second anyway, so there's no need for internal refresh. Doing a little reading just now, it looks like the DVI data stream is a simple raster scan. It even apparently has "blanking intervals," though they couldn't possibly be for same purpose as on a CRT.

DVI's timing and blanking intervals are the same as VGA's. I believe it was designed this way to make the modification to the video cards easier, and to facilitate dual-output DVI / VGA video cards. (so the VGA port is basically just the DVI port with an extra D2A converter in the path.)