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ATI fglrx proprietary driver problems

November 14, 2008

I know many hate ATI+Linux, but I’m not a gamer and usually run linux by command line only. I have a ATI 9600 Pro AGP video card that I’ve been using in one of my MythTV frontend’s for years. In order to play high definition resolutions (720p 1080i) I need to use ATI’s proprietary linux driver, fglrx. And it works well for that, as well as my nVidia card in my other frontends. I end up rebuilding my frontends maybe every 9-12 months, just for fun. That’s where nVidia outperforms ATI. The ATI driver can be much more difficult to get running properly, partly because they change it so drastically, at least it’s different every time I rebuild a frontend.
The latest problem is the driver and assocated configuration tool, aticonfig. fglrx now basically ignores any options in xorg.conf except for the options available by the aticonfig tool. For example, it reads EDID information from your display and will only output a mode that your display allows. Sounds great, right? Sure, assuming fglrx is reading EDID properly, or if at all. If it can’t read EDID, the max resolution is 1024×768. You can’t tell it to ignore EDID and specify a modeline instead. This happened to me. I tried every possible combination of settings in xorg.conf, reinstalled the driver, from RPM and the installer from ATI’s website. But EDID came up as invalid according to /var/log/Xorg.0.log.
Finally figured out there is a file that the driver uses that can become incorrect or corrupt. I deleted this file:

# rm /etc/ati/amdpcsdb

and everything started working great. X came up at 1080p and MythTV works great, although openGL menu transitions are a little slow with my card, so I turned that off. Apparently its possible to modify settings in that file, which overrides anything in xorg.conf.

Filed under: Hardware, Linux, MythTV |

1 Comment

  1. jdkbx December 16, 2008 @ 10:08 am

    wow,

    just came across this. I had a display replaced, so i was running for 3 days only with one monitor attached, and used a one screen config during that time. After i connected the replacement i copied the original xorg.conf back, but i just wouldn’t work. Fglrx was basically ignoring anything in xorg.conf.
    Until i deleted this file “/etc/ati/amdpcsdb”. Now it’s working as it used to.

    Thx, saved my day.