Fault-tolerant microcontroller units (MCU) are becoming a standard requirement in the automotive industry. In this paper, we research three fault-tolerant architectures for automotive applications. Then a fully study and comparison in reliability has been applied to these different architectures through markov modeling. The analysis shows that the enhanced dual-CPU architecture outperforms higher reliability which reduces the risk 6.3 times better than the dual-CPU lock-step architecture at most, 2.7 times better than the triple module redundancy architecture.