  The centrality dependence of the midrapidity charged-particle multiplicity
density ($|\eta|$$<$1) is presented for Au+Au and Cu+Cu collisions at RHIC over
a broad range of collision energies. The multiplicity measured in the Cu+Cu
system is found to be similar to that measured in the Au+Au system, for an
equivalent N$_{\rm part}$, with the observed factorization in energy and
centrality still persistent in the smaller Cu+Cu system. The extent of the
similarities observed for bulk particle production is tested by a comparative
analysis of the inclusive transverse momentum distributions for Au+Au and Cu+Cu
collisions near midrapidity. It is found that, within the uncertainties of the
data, the ratio of yields between the various energies for both Au+Au and Cu+Cu
systems are similar and constant with centrality, both in the bulk yields as
well as a function of p$_{\rm T}$, up to at least 4 GeV/$c$. The effects of
multiple nucleon collisions that strongly increase with centrality and energy
appear to only play a minor role in bulk and intermediate transverse momentum
particle production.
