We investigate numerical methods for passive
model reduction of linear dynamical systems. This
is an important task in circuit simulation when
modeling parasitic effects of interconnect. We will
show how positive real balancing, based on balancing
the solutions of two algebraic Riccati equations,
can be used for passive model reduction
of large-scale systems on parallel computers. Numerical
experiments demonstrate the performance
of the parallel algorithms using several examples
from circuit simulation.