I'm not sure in what world a 1.5 GHz four core machine is faster than a 64 core 2.0 GHz machine with not only 1 MB L2 cache per four cores, but 4 MB L3 cache pe

I'm not sure in what world a 1.5 GHz four core machine is faster than a 64 core 2.0 GHz machine with not only 1 MB L2 cache per four cores, but 4 MB L3 cache per four cores, all 64 MB of which is usable by a single (or a few cores) when running code without many threads. The Pioneer uses the C910 core (64 of them, as noted), not U74. Perhaps you were thinking of the old early 2021 HiFive Unmatched?