737NG EFIS Control Panel failure
On the 737NG an EFIS control panel failure will give a 'DISPLAYS CONTROL PANEL' on the PFD.
However it also blanks the altimeter on the failed side and displays the ALT flag until you move the CONTROL PANEL select switch to the controller that hasn't failed.
My question is why does the Altimeter blank? It is the EFIS controller that has failed both DEU's are functioning normally and providing independent, correct data.
Why remove primary flight data for no reason except as a bizarre attention getting exercise (The Amber Caution on the PFD should be enough). Is there a black magic reason behind it or just another Boeing thing?