  We discuss the link between dark matter halos hosting the first PopIII stars
formed at redshift z > 40 and the rare, massive, halos that are generally
considered to host bright z~6 quasars. We show that within the typical volume
occupied by one bright high-z QSO the remnants of the first several thousands
PopIII stars formed do not end up in the most massive halos at z~6, but rather
live in a large variety of environments. The black hole seeds planted by these
very first PopIII stars can easily grow to M > 10^{9.5} Msun by z=6 assuming
Eddington accretion with radiative efficiency epsilon~0.1. Therefore quenching
of the accretion is crucial to avoid an overabundance of supermassive black
holes. We implement a simple feedback model for the growth of the seeds planted
by PopIII stars and obtain a z~6 BH mass function consistent with the observed
QSO luminosity function.
