  We reexamine the dynamics of the Olami, Feder and Christensen (OFC) model. We
show that, depending on the dissipation, it exhibits two different behaviors
and that it can or cannot show self - organized - criticality (SOC) and/or
synchronization. We also show that while the Feder and Feder model perturbed by
a stochastic noise is SOC and has the same exponent for the distribution of
avalanche sizes as the OFC model, it does not show synchronization. We conclude
that a relaxation oscillator system can be synchronized and/or SOC and that
therefore synchronization is not necessary for criticality in these models.
