multi monitor/multi card status

Dave Airlie airlied at
Sun Oct 11 01:30:58 PDT 2009

On Sun, Oct 11, 2009 at 9:15 AM, Csillag Kristof
<csillag.kristof at> wrote:
> Dear all,
> Please help me assess the general situation. I am trying to get a
> multimonitor/multicard setup work with ati cards and the free radeon driver.
> Here is my current understanting of how things go. Those with the proper
> knowledge/authority, please confirm/correct/deny the following statements!
> 1. Monitors on the same GPU can be united into a big desktop using
> randr. Unfortunately, most GPU-s can only drive at most 2 monitors.
>    There are cards like the FireMV 2400, which have 4 outputs, but they
> are internally two GPUs, so they do not count.
> Q: are there any radeon cards with more than two digital outputs
> connected to the same GPU?
> 2. To unite monitors connected to different GPUs (on he X server level),
> one needs Xinerama.
> 3. Uniting a monitor from one GPU and an other monitor from an other GPU
> works fine with Xinerama.
> 4. If one wants to use Xinerama to unite monitors from different GPUs,
> and there is a GPUs which has more that one monitors connected to then,
> it is not allowed to use randr to unite these monitors (before uniting
> them with the rest, on the different GPUs), because randr and Xinerama
> do not mix. Therefore, instead of the normal (randr) mode, one needs to
> go with Zaphod-mode.
> 5. Zaphod more rarely gets any testing, and tends to be broken. (Right
> now it seems to be.)

Mostly true up until there, zaphod on radeon should be working fine,
under KMS and under non-KMS, I test it at least once per Fedora release

However there are various issues with older X's and two cards such
as secondary posting breakage, hangs on X server exit with two cards,
these should all be solved in a KMS environment,

the only remainging thing that zaphod doesn't do at the moment is let you
configure which outputs go where, which depending on the BIOS output
ordering can be a bit
of a pain, esp if TV is detected second.


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