  We present timing analysis of {\emph{RXTE}}-PCA and {\emph{INTEGRAL}}-ISGRI
observations of X Per between 1998 and 2010. All pulse arrival times obtained
from the {\emph{RXTE}}-PCA observations are phase connected and a timing
solution is obtained using these arrival times. We update the long-term pulse
frequency history of the source by measuring its pulse frequencies using
{\emph{RXTE}}-PCA and {\emph{INTEGRAL}}-ISGRI data. From the {\emph{RXTE}}-PCA
data, the relation between frequency derivative and X-ray flux suggests
accretion via the companion's stellar wind. On the other hand, detection of the
transient QPO feature peaking at $\sim 0.2$ Hz suggests the existence of an
accretion disc. We find that double break models fit the average power spectra
well, which suggests that the source has at least two different accretion flow
components dominating the overall flow. From the power spectrum of frequency
derivatives, we measure a power law index of $\sim -1$ which implies that on
short time scales disc accretion dominates over noise, while on time scales
longer than the viscous time scales the noise dominates. From pulse profiles,
we find a correlation between pulse fraction and count rate of the source.
