Terahertz band communications is a promising enabler technology for Wireless-Networks-on-Chip. However, the backward compatibility issues appear when considering the massive production. Motivated by this, we proposed a novel 3D x86-compatible CPU architecture with THz assisted wireless links between the cores and the shared cache. Our cross-disciplinary analysis reveals that up to 200 cores can be supported by the THz-enabled wireless-network-on-chip
Vitaly Petrov, Dmitri Moltchanov, Maria Komar, Alexander Antonov, Pavel Kustarev, Shaloo Rakheja, Yevgeni Koucheryavy
Massive multi-core processing has recently attracted significant attention from the research community as one of the feasible solutions to satisfy constantly growing performance demands. However, this evolution path is nowadays hampered by the complexity and limited scalability of bus-oriented intra-chip communications infrastructure. The latest advantages of terahertz (THz) band wireless communications providing extraordinary capacity at the air interface offer a promising alternative to conventional wired solutions for intra-chip communications. Still, to invest resources in this field manufacturers need a clear vision of what are the performance and scalability gains of wireless intra-chip communications. Using the comprehensive hybrid methodology combining THz ray-tracing, direct CPU traffic measurements, and cycle-accurate CPU simulations, we perform the scalability study of x86 CPU design that is backward compatible with the current x86 architecture. We show that preserving the current cache coherence protocols mapped into the star wireless communications topology that allows for tight centralized medium access control a few hundreds of active cores can be efficiently supported without any notable changes in the x86 CPU logic. This important outcome allows for incremental development, where THz-assisted x86 CPU with a few dozens of cores can serve as an intermediate solution, while the truly massive multi-core system with broadcast-enabled medium access and enhanced cache coherence protocols can be an ultimate goal.
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