IEEE In inverter-based microgrids, individual inverters operate usually with its own digital processor. The clocks used to generate the time signals of these processors differ from each other due to clock drifts. This paper analyzes the impact that the drifts of the processors clocks produce on the operation of inverter-based islanded microgrids. Several communication-free secondary control schemes are considered, which avoid well-known problems caused by digital communication networks. Active power sharing and frequency regulation are the metrics used to evaluate the performance of the secondary control schemes. The study reveals advantages, drawbacks, and practical limitations of the control schemes caused by the clock drifts. Therefore, it facilitates the selection of the most suitable control scheme for the practical deployment of microgrids. The theoretical results are validated by experimental tests in a laboratory microgrid equipped with three inverters and three digital signal processors driven by autonomous internal clocks.