Comment 9 for bug 575496

(In reply to comment #4)
> > Older radeons rarely had edids for the LVDS panel, the vbios lvds
> > table only has the panel modeline, not the physical size.
>
> The old radeon driver (back in the xfree86 days) did know that my
> laptop’s screen was 12”×9”. I originally added --dpi 133 to my X
> startup scripts only because the integer conversions between inch
> (for dpi) and mm (for dimensions) led to rounding errors.

The driver did not even have support for reading edids from LCD panels at that time so it must have been some different behaviour in the xserver rather than the driver.