  The fluid and solid equations of state for hard parallel squares and cubes
are reinvestigated here over a wide range of densities. We use a novel
single-speed version of molecular dynamics. Our results are compared with those
from earlier simulations, as well as with the predictions of the virial series,
the cell model, and Kirkwood's many-body single-occupancy model. The
single-occupancy model is applied to give the absolute entropy of the solid
phases just as was done earlier for hard disks and hard spheres. The excellent
agreement found here with all relevant previous work shows very clearly that
configurational properties, such as the equation of state, do not require the
maximum-entropy Maxwell-Boltzmann velocity distribution. For both hard squares
and hard cubes the free-volume theory provides a good description of the
high-density solid-phase pressure. Hard parallel squares appear to exhibit a
second-order melting transition at a density of 0.79 relative to close-packing.
Hard parallel cubes have a more complicated equation of state, with several
relatively-gentle curvature changes, but nothing so abrupt as to indicate a
first-order melting transition. Because the number-dependence for the cubes is
relatively large the exact nature of the cube transition remains unknown.
