https://bugs.freedesktop.org/show_bug.cgi?id=42808
--- Comment #4 from samit vats hysvats@gmail.com 2011-11-11 04:12:54 PST --- (In reply to comment #3)
This may be because the primary device is the integrated Intel GPU, not the Radeon one. Possible solutions might be removing the Section "Device" for the radeon driver (letting it be auto-loaded via the ati driver) or adding a BusID stanza to it.
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Added BusID in Device section for radeon gpu but again startx fails with following message : "Unable to find connected outputs - setting 1024x768 initial framebuffer" Its a Dell Inspiron Laptop.