  Recent results suggest that the initial mass function (IMF) of globular
clusters (GCs) is metallicity and density dependent. Here it is studied how
this variation affects the initial masses and the numbers of core collapse
supernovae (CCSNe) required to reproduce the observed iron spreads in GCs. The
IMFs of all of the investigated GCs were top-heavy implying larger initial
masses compared to previous results computed assuming an invariant canonical
IMF. This leads to more CCSNe being required to explain the observed iron
abundance spreads. The results imply that the more massive GCs formed at
smaller Galactocentric radii, possibly suggesting in-situ formation of the
population II halo. The time until star formation (SF) ended within a proto-GC
is computed to be 3.5 - 4 Myr, being slightly shorter than the 4 Myr obtained
using the canonical IMF. Therefore, the impact of the IMF on the time for which
SF lasts is small.
