Reconfigurable: Self Adaptive Fault Tolerant Cache Memory for DVS enabled Systems

Abstract

Processor caches play a critical role in the performance of today"s computer systems. As technology scales, due to manufacturing defects and process variations a large number of cells in a cache is expected to be faulty. The number of faulty cells varies from die to die and in the field of the application depends on the operating conditions (e.g., supply voltage, frequency). Several techniques have been proposed to tolerate faults in caches. A drawback of the redundancy based techniques is that the amount of redundancy is decided at the design time targeting a maximum number of faults, so in cases of a small number of faults (e.g., in the nominal supply voltage in a system with DVS) only a part of the redundant resources is used. In this paper we propose a new reconfigurable-self adaptive fault tolerant cache scheme. The unique characteristic of our scheme is that it uses its resources for both the reduction of the misses caused by the faulty blocks as well as for the reduction of conflict misses, depending on the number of faults, their distribution in the cache, and the running application. Our experimental results for a wide range of scientific applications and a plethora of fault maps with different SRAM failure probabilities reveal that our proposal can achieve significant benefits.