IPC (Instructions Per Cycle)
Instructions Per Clock — a CPU performance metric: how many instructions retire per clock cycle on average. Modern CPUs (Apple M3, AMD Zen 4, Intel Lion Cove) reach ~4-5 IPC on typical workloads. Confusingly similar to "Inter-Process Communication" — different concept.
Total performance = IPC × frequency. When frequency scaling stalled (2005, Dennard scaling dead), IPC became the primary improvement vector. Microarchitectural changes for higher IPC: wider execution pipeline, more reorder-buffer entries, better branch predictor, larger L1/L2 cache. The Apple M series has high IPC but low frequency (4 GHz vs Intel's 5.5+). The x86 vs ARM IPC debate — Apple's M design wins per watt, x86 wins per frequency. ICC ("Instructions per Cycle") is a synonym.