Correction prediction: Reducing error correction latency for on-chip memories

The reliability of on-chip memories (e.g., caches) determines their minimum operating voltage (V_min) and, therefore, the power these memories consume. A strong error correction mechanism can be used to tolerate the increasing memory cell failure rate as supply voltage is reduced. However, strong error correction often incurs a high latency relative to the on-chip memory access time. We propose correction prediction where a fast mechanism predicts the result of strong error correction to hide the long latency of correction. Subsequent pipeline stages execute using the predicted values while the long latency strong error correction attempts to verify the correctness of the predicted values in parallel. We present a simple correction prediction implementation, CP, which uses a fast, but weak error correction mechanism as the correction predictor. Our evaluations for a 32KB 4-way set associative SRAM L1 cache show that the proposed implementation, CP, reduces the average cache access latency by 38%-52% compared to using a strong error correction scheme alone. This reduces the energy of a 2-issue in-order core by 16%-21%.