All Semi Vendors do have multi core CPUs in their portfolio and adding new devices every day. This is the only possibility to grow performance and fulfill Moore's law. Multi core offers a wide variety of possibilities to reduce hardware complexity, reduce power consumption, shrink board space, expand functionality and performance. On the other hand the software complexity goes up and this directly affects the ability to achieve a certified system. The main trend as of today and in the future is the rising number of cores in a single chip and the increasing functionality of the software. As this trend does not stop at safety critical systems, the System/Solution Architects have to question themselves how to guarantee data integrity, robustness, robust portioning, avoid multi point of failures and race conditions. This presentation will highlight ideas, do's and don'ts for those who will design a safety critical multi Core system today or in the near future. The hardware design and the RTOS design has to go hand in hand to guarantee a effective use of the CPU performance and to assure certifiable safety critical system.