Popcorn is a Linux based replicated-kernel Operating System (OS). Popcorn was conceived as a research OS for a wide class of future heterogeneous-ISA hardware. Because of the novelty of such hardware, in which diverse OS-capable CPUs are glued together, it is not clear what level of memory sharing will be provided across these CPUs. In this paper, the authors consider a setup in which diverse CPUs do not share memory. They addressed the problem of providing a coherent replicated process address space amongst different kernels, running on those CPUs, by proposing a new page coherency protocol.