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

fireworks mode
 n.

    1. The mode a machine is sometimes said to be in when it is performing a 
    crash and burn operation.

    2. There is (or was) a more specific meaning of this term in the Amiga
    community. The word fireworks described the effects of a particularly
    serious crash which prevented the video pointer(s) from getting reset at
    the start of the vertical blank. This caused the DAC to scroll through the
    entire contents of CHIP (video or video+CPU) memory. Since each bit plane
    would scroll separately this was quite a spectacular effect.


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

fireworks mode

   The mode a machine is sometimes said to be in when
   it is performing a crash and burn operation.

   [Jargon File]