  The median observed velocity width v_90 of low-ionization species in damped
Ly-alpha systems is close to 90 km/s, with approximately 10% of all systems
showing v_90 > 210 km/s at z=3. We show that a relative shortage of such
high-velocity neutral gas absorbers in state-of-the-art galaxy formation models
is a fundamental problem, present both in grid-based and particle-based
numerical simulations. Using a series of numerical simulations of varying
resolution and box size to cover a wide range of halo masses, we demonstrate
that energy from gravitational infall alone is insufficient to produce the
velocity dispersion observed in damped Ly-alpha systems, nor does this
dispersion arise from an implementation of star formation and feedback in our
highest resolution (~ 45 pc) models, if we do not put any galactic winds into
our models by hand. We argue that these numerical experiments highlight the
need to separate dynamics of different components of the multiphase
interstellar medium at z=3.
