  We first clarify timing issues of non-uniform sampling intervals regarding a
5 GS/s fast pulse sampling module with DRS4. Calibration strategy is proposed,
and as a result, the waveform timing performance is improved to be below 10 ps
RMS. We then further evaluate waveform timing performance of the module by
comparing with a 10 GS/s oscilloscope in a setup with plastic scintillators and
fast PMTs. Different waveform timing algorithms are employed for analysis, and
the module shows comparable timing performance with that of the oscilloscope.
