Comment 3 for bug 1235201

I suspect one of the key commits is:

commit dc498b433f36af5d2de3065e7c64cdb575385d81
Author: Adam Jackson <email address hidden>
Date: Mon Feb 8 15:23:04 2010 -0500

    xfree86: If the driver found modes on an output, don't add more

    Inferring modes from sync ranges is only valid if the monitor says it's
    valid. If the monitor says it's valid, then we'll have already added
    those modes during EDID block parse. If it doesn't, then we should
    believe it.

    If there's no EDID for an output, but sync ranges from the config, we'll
    still add default modes as normal.

    Reviewed-by: Alex Deucher <email address hidden>
    Signed-off-by: Adam Jackson <email address hidden>