  We report on the status of a program of generating and using configurations
with four flavors of dynamical quarks, using the HISQ action. We study the
lattice spacing dependence of physical quantities in these simulations, using
runs at several lattice spacings, but with the light quark mass held fixed at
two tenths of the strange quark mass. We find that the lattice artifacts in the
HISQ simulations are much smaller than those in the asqtad simulations at the
same lattice spacings and quark masses. We also discuss methods for setting the
scale, or assigning a lattice spacing to ensembles run at unphysical
parameters.
