Larry Hardesty, MIT News, First new cache-coherence mechanism in 30 years, here. PRAM was 30 years early.
What Yu and his thesis advisor — Srini Devadas, the Edwin Sibley Webster Professor in MIT’s Department of Electrical Engineering and Computer Science — realized was that the physical-time order of distributed computations doesn’t really matter, so long as their logical-time order is preserved. That is, core A can keep working away on a piece of data that core B has since overwritten, provided that the rest of the system treats core A’s work as having preceded core B’s.
The ingenuity of Yu and Devadas’ approach is in finding a simple and efficient means of enforcing a global logical-time ordering. “What we do is we just assign time stamps to each operation, and we make sure that all the operations follow that time stamp order,” Yu says.
Terry Tao, What’s New, 275A, Notes 0: Foundations of probability theory, here.