How configure dual head on different graphic cards?

[Frantisek Hanzlik]

I'm trying configure two monitors on my several desktop systems
(Fedora 12 or Fedora 13 beta i686, kernels 2.6.31/2.6.32/2.6.33,
Xorg server 1.7.5.901, XRandR 1.3, desktops have integrateg graphics
(Intel G35 or Radeon Xpress 200G[RS480]), 1-4GB RAM, PCIe busses).

Somewhere on net I found, X server version >= 1.7 can support multiple
different graphics card (not only dual/triple link ones), then I tried
configure systems with internal + one add-on card.
Until now I'm unsuccessful. Fedora's tool "system-config-display" do not
detect secondary video card, I experiment with some dynamic configuration
(xrandr) or static with xorg.conf, but without success. Some experiments
with adding dual-link MGA G550 card wasn't successful too, I wasn't able
supress integrated graphic card.

As I have no big experience with actual up-to-date X configuration,
please, is there any cookbook/Howto how do this tasks? It would be best
with some troubleshooting knowledge. What I found on net, was all about
dual-link cards and RandR 1.2.
Or, for some direct suggestion from this list, which information I should
post here?

Thanks in advance, Franta Hanzlík