The Jargon File (version 4.4.7, 29 Dec 2003):

raster blaster
 n.

    [Cambridge] Specialized hardware for bitblt operations (a blitter).
    Allegedly inspired by ?Rasta Blasta?, British slang for the sort of
    portable stereo Americans call a ?boom box? or ?ghetto blaster?.


The Free On-line Dictionary of Computing (30 December 2018):

raster blaster

    (Cambridge) Specialised hardware for
   bitblt operations (a blitter).  Allegedly inspired by
   "Rasta Blasta", British slang for the sort of portable stereo
   Americans call a "boom box" or "ghetto blaster".

   [Jargon File]

   (1995-03-22)