Heterogeneous Lockstep (Hecocefta)—is an advanced, more secure variant of traditional lockstep processors, suitable for applications requiring the highest level of automotive safety integrity (ASIL-D). While conventional lockstep processors primarily guard against natural and random failures, Hecocefta also protects against cyber exploits. Conceptually, Hecocefta is related to the BFT++ family. With minimal additional logic, a three-core Hecocefta design can be configured to implement BFT++ v.4—codenamed RumRaisin—directly on a chip. RumRaisin, an evolution of Vanilla BFT++ (v.1), achieves diversity by employing different processor architectures (ISAs). Hecocefta’s key contribution is a method for synchronizing two distinct processor architectures on a cycle-by-cycle basis.