HP Pavilion 27xi Monitor: Display problem Mac Mini running Yosmite

Adjusting overscan helps scaling, but pixelation and poor image quality is not changed (very blurry)

Using VGA/mini display route with same devices, image quality if far better showing that somehow mini conncected to HP monitor via HDMI could be improved via driver update.

Is there a driver update for Yosmite?

Only drivers found were for Windows:

http://support.hp.com/us-en/product/HP-Pavilion-27-inch-Displays/7274719/model/5304250/drivers

Please help