  Context. The dissipation process responsible for the long gamma-ray burst
(GRB) prompt emission and the kind of dynamics that drives the release of
energy as a function of time are still key open issues. We recently found that
the distribution of the number of peaks per GRB is described by a mixture of
two exponentials, suggesting the existence of two behaviours that turn up as
peak-rich and peak-poor time profiles.
  Aims. Our aims are to study the distribution of the number of peaks per GRB
of the entire catalogue of about 3000 GRBs observed by the Fermi Gamma-ray
Burst Monitor (GBM) and to make a comparison with previous results obtained
from other catalogues.
  Methods. We identified GRB peaks using the MEPSA code and modelled the
resulting distribution following the same procedure that was adopted in the
previous analogous investigation.
  Results. We confirm that only a mixture of two exponentials can model the
distribution satisfactorily, with model parameters that fully agree with those
found from previous analyses. In particular, we confirm that (21 +- 4)% of the
observed GRBs are peak-rich (8 +- 1 peaks per GRB on average), while the
remaining 80% are peak-poor (2.12 +- 0.10 peaks per GRB on average).
  Conclusions. We confirm the existence of two different components, peak-poor
and peak-rich GRBs, that make up the observed GRB populations. Together with
previous analogous results from other GRB catalogues, these results provide
compelling evidence that GRB prompt emission is governed by two distinct
regimes.
