  We examine the possibility that galactic halos are collisionless ensembles of
scalar field ``massive compact halo objects'' (MACHOs). Using mass constraints
from MACHO microlensing and from theoretical arguments on halos made up of
massive black holes, as well as demanding also that scalar MACHO ensambles of
all scales do not exhibit gravothermal instability (as required by consistency
with observations of LSB galaxies), we obtain the range: $m\alt 10^{-7}
M_\odot$ or $30 M_\odot\alt m\alt 100 M_\odot$. The rather narrow mass range of
large MACHOs seems to indicate that the ensambles we are suggesting should be
probably made up of scalar MACHOs in the low mass range (``mini--MACHOs''). The
proposed model allows one to consider a non--baryonic and non--thermal
fundamental nature of dark matter, while at the same time keeping the same
phenomenology of the CDM paradigm.
