Temporal Reference Scouting Logic for PVT Reliable Logic Computation-in-Memory

Non-volatile memory (NVM) based Compute-in-Memory (CiM) enables energy-efficient in-situ execution of logic operations. However, its reliability is severely degraded by process, voltage, temperature (PVT) variations, IR-drop, aging, and sensing offsets. Scouting logic-based Boolean operations, which determine the results by comparing the data column against a reference threshold, are particularly vulnerable because the conventional reference is generated from static resistance blocks and therefore cannot track PVT-induced shifts in the data path, leading to unacceptably large bit-error rate (BER). We propose Temporal-Reference Scouting Logic (TRSL), a capacitor-based calibration scheme that derives the reference directly from the same devices used for the logic operation. A threshold pattern is temporarily written, sampled onto a capacitor, overwritten by operand data, and then compared while accounting for predictable leakage. Since the reference voltage and the data voltage are generated from the same devices in consecutive cycles, TRSL cancels device variability and naturally tracks PVT drift. Thereby reducing BER by ≈3 orders of magnitude, enabling reliable NVM–CiM logic. ... mehrSystem-level evaluation using NVM–CiM extensions in gem5 shows that TRSL reduces software-visible failures by nearly 21× across workloads while incurring only modest latency overhead (≈6%) compared to standard Scouting logic.