Cerebras makes CPUs with ~1 million cores, and they're inferring on that not on GPUs. It's an entirely different architecture which means no network involved. It's possible they're doing this significantly from CPU caches rather than HBM as well.
I recommend the TechTechPotato YouTube videos on Cerebras to understand more of their chip design.
I recommend the TechTechPotato YouTube videos on Cerebras to understand more of their chip design.