There’re 4 cores on the chip, but only two cores, one of CM4 and RI5CY, one of CM0+ and Zero-riscy, are recommended because of the two sides feature of Message Unit (MU) module. One side is CM4 or Ri5cy and another side is CM0+ or zero-riscy. In theory, you can use 4 cores together, but MU will only manage two cores. Your software needs to process the communication with additional cores. If you want to try it, you can reference the 2.3 System Boot and Reset in the Develop a Multicore Application for RV32M1-VEGA application note for more information .