  We present a power spectral analysis of a 100 ksec XMM-Newton observation of
the narrow line Seyfert 1 galaxy Ark~564. When combined with earlier RXTE and
ASCA observations, these data produce a power spectrum covering seven decades
of frequency which is well described by a power law with two very clear breaks.
This shape is unlike the power spectra of almost all other AGN observed so far,
which have only one detected break, and resemble Galactic binary systems in a
soft state. The power spectrum can also be well described by the sum of two
Lorentzian-shaped components, the one at higher frequencies having a hard
spectrum, similar to those seen in Galactic binary systems. Previously we have
demonstrated that the lag of the hard band variations relative to the soft band
in Ark 564 is dependent on variability time-scale, as seen in Galactic binary
sources. Here we show that the time-scale dependence of the lags can be
described well using the same two-Lorentzian model which describes the power
spectrum, assuming that each Lorentzian component has a distinct time lag. Thus
all X-ray timing evidence points strongly to two discrete, localised, regions
as the origin of most of the variability. Similar behaviour is seen in Galactic
X-ray binary systems in most states other than the soft state, i.e. in the
low-hard and intermediate/very high states. Given the very high accretion rate
of Ark 564 the closest analogy is with the very high (intermediate) state
rather than the low-hard state. We therefore strengthen the comparison between
AGN and Galactic binary sources beyond previous studies by extending it to the
previously poorly studied very high accretion rate regime.
