Embodiments of the invention relate to a driven-frequency processor core. It comprises at least one processor, a non-volatile memory comprising a startup program, a bridge interconnecting buses linking the various components of said processor core, an interface component. The non-volatile memory comprises at least two frequency-related configurations each corresponding to an operating mode of the buses and/or of the components of said processor core. The non-volatile memory comprises an item of information which makes it possible to determine which operating mode should be used, said item of information being read by the interface component so as to determine the chosen mode. The interface component generates one or more clock signals, the frequency of said generated clock signals corresponding substantially to that described by the configuration of the chosen mode. The clock signals drive the buses and/or the components of said processor core. Embodiments of the invention also relate to a method for starting-up said processor core in a programmed mode. In particular, the invention is applied to processor cores embedded in aircraft.