This document discusses building cache-coherent scaleout systems using OmniXtend. It describes the OmniXtend architecture, which uses a fully open cache-coherence protocol that works over Ethernet. It then discusses the OmniXtend reference design, compute node architecture, address space, and hardware design. It also covers the single operating system and independent nodes system models, the unified boot process, and status of the current implementation. Lastly, it proposes ways to further develop the system through simulation, emulation, and future work.