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That pesky video problem

A couple of weeks back I posted about a problem with rippling on the VGA out image from my Thinkpad T41 (Radeon Mobility 7500). I have had a chance to play around with it a bit, and I have some new data (and a
voodoo workaround involving the sacrifice of a goat and two chickens).

(1) The ripples appear in vertical bands.

(2) Autosynching the external monitor usually helps, at least somewhat (when it is possible).

(3) Booting with the external monitor attached seems to solve the problem. Once I've done that, I can suspend/resume or move to another external monitor without seeing the problem. Reboot without the external monitor, problem returns. Toggling the external DAC with radeontool has no effect.

(4) Unfortunately, when X starts with the external monitor attached, it sets the external monitor's resolution to something very low, like 640x480 (even though the laptop panel is 1024x768). To solve that problem, I must disconnect the external monitor, force X to restart, then plug the monitor back in. (That gets the resolution right, but doesn't cure the ripples if they are there--not surprising, as the ripples appear on VCs as well as in

So, any other suggestions about where the problem may lie?

And any suggestions on how to fix (4)?


		Matthew Saltzman

Clemson University Math Sciences
mjs AT clemson DOT edu

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