iMac Resolution Issue

Eric Dunbar eric.dunbar at
Sat Oct 29 10:44:24 UTC 2005

Hi Mr. Knisely,

which iMac are you running specifically? You should be able to deduce
that either by booting into Mac OS (use the Install/Rescue CD or boot
into another partition and run "Apple System Info" (or whatever it was
called)), or by looking on a sticker on the outside of the computer,

You are *not* running a Radeon graphics card in your iMac. Only the
latest and greatest G5s are running Radeons (and, you're unlikely to
be running Linux on one of those ;-)!!!

You are probably using a much earlier flavour of ATI and it should be
_fully_ supported by Ubuntu!!!

You're probably going to have to fiddle with the xorg.conf file where
your resolutions are specified.

If you haven't already figured out your problem, can  you please
repost your original question along with some details (you'll get much
more helpful answer if your provide sufficient info). Also, you may
want to past PART of your xorg.conf file here (the section with
resolution info). That way the "experts" will be able to recognise
problems in your config. (but, it really is iimportant to know which
Mac you're using... tray loading (which Rev A, B, C or D?)

There should only be THREE resolutions for the iMac: 640*480, 800*600
and 1024*768!


On 10/26/05, Scott J. Henson <scotth at> wrote:
> Hash: SHA1
> Mr. Knisely wrote:
> > I've got a tray loading iMac that I've loaded the PPC verion of Ubuntu
> > on. My display settings are very low, under 640x480 but the exact number
> > escapes me at the moment.
> >
> > I've seen others have run into this issue before but I've not found the
> > solution for it. Anyone have any suggestions?
> I believe your running a radeon of some sort and your using the xorg
> radeon driver.  So, to solve your problem I would recommend enabling
> DDC.  If you type 'man radeon' at a command prompt, youll see all the
> options you can use.  The one your looking for is as follows
>       Option "DDCMode" "boolean"
>               Force to use the modes queried from the connected monitor.
>               The default is off.
> So youll want to add that to your device section of your /etc/X11/xorg.conf
> Then you should be able to use the resolution capplet under
> System->Preferences->Screen Resolution to set a higher resolution.

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