Source : Free On-Line Dictionary of Computing

Plug Compatible Manufacturer
     
         (PCM) A manufacturer of equipment that some other
        manufacturer's system can identify and work with.  The PCM's
        device replaces the original manufacturer's.
     
        Most PCMs competed with {IBM}.  PCM devices normally offer a
        cost-performance benefit over the original device.  For
        example, several PCM versions of the {Direct-Access Storage
        Device} {IBM 3350} offered twice the storage and improved data
        access (dual port).
     
        Plug compatible devices include replacement {CPU}s, such as
        the {Hitachi 7/90} series (which could be substituted for {IBM
        3090} series processors), {I/O} subsystems, and {dumb
        terminals} like the {IBM 3270}.
     
        [Used outside mainframe market?]
     
        (2003-06-24)