The ARINC 653 standard imposes stringent timing and behavioral requirements on avionic software applications. As multicore systems gain interest in aerospace applications, there is a growing need for tools to aid in their design and implementation. To address this challenge, we propose A653MSim, a simulation solution that enables the validation of multicore ARINC 653-compliant system functionality. Our validation demonstrates that A653MSim not only ensures functional compliance with the ARINC 653 standard but also exhibits linear scalability as the number of simulated cores increases.