When Two Cores See Different Realities: The Cache Coherence Problem MESI Was Built to Solve
In 1984, researchers at the University of Illinois published a paper that would quietly shape every multicore processor built since. Mark Papamarcos and Janak Patel proposed a solution to a problem that didn’t seem urgent at the time—how to keep data consistent when multiple processors each have their own cache. Today, with CPUs packing dozens of cores, their invention runs on billions of devices, silently orchestrating a dance of state transitions every time one core writes to memory and another needs to read it. ...