I'm not sure what the cores actually are, but the PEZY chips have 1024 and 2048 cores, end Epiphany V taped out at 1024. There are others, at least Kalray and Sunway (Taihulight), with 256 cores. They may not be sufficiently general-purpose -- Taihulight is imbalanced against memory bandwidth -- but can clearly do well on the right sort of problem.