The Free On-line Dictionary of Computing (19 January 2023):

killer poke

   A recipe for inducing hardware damage on a machine via
   insertion of invalid values (see poke) into a
   memory-mapped control register; used especially of various
   fairly well-known tricks on bitty boxes without hardware
   memory management (such as the IBM PC and Commodore PET)
   that can overload analog electronics in the monitor.

   See also HCF.

   (1994-11-04)


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

killer poke
 n.

    A recipe for inducing hardware damage on a machine via insertion of invalid
    values (see poke) into a memory-mapped control register; used esp. of
    various fairly well-known tricks on bitty boxes without hardware memory
    management (such as the IBM PC and Commodore PET) that can overload and
    trash analog electronics in the monitor. See also HCF.