Source : Free On-Line Dictionary of Computing

chicken head
     
        The {Commodore} Business Machines logo, which strongly
        resembles a poultry part.  Rendered in ASCII as "C=".  With
        the arguable exception of the {Amiga}, Commodore's computers
        are notoriously crocky little {bitty box}es (see also
        {PETSCII}).  Thus, this usage may owe something to Philip
        K. Dick's novel "Do Androids Dream of Electric Sheep?"  (the
        basis for the movie "Blade Runner"; the novel is now sold
        under that title), in which a "chickenhead" is a mutant with
        below-average intelligence.
     
        [{Jargon File}]