A fault tolerant cache architecture for sub 500mV operation: Resizable Data Domposer Cache (RDC-Cache)

In this paper we introduce Resizable Data Composer-Cache (RDC-Cache). This novel cache architecture operates correctly at sub 500 mV in 65 nm technology tolerating large number of Manufacturing Process Variation induced defects. Based on a smart relocation methodology, RDC-Cache decomposes the data that is targeted for a defective cache way and relocates one or few word to a new location avoiding a write to defective bits. Upon a read request, the requested data is recomposed through an inverse operation. For the purpose of fault tolerance at low voltages the cache size is reduced, however, in this architecture the final cache size is considerably higher compared to previously suggested resizable cache organizations [2][3]. The following three features a) compaction of relocated words, b) ability to use defective words for fault tolerance and c) "linking" (relocating the defective word to any row in the next bank), allows this architecture to achieve far larger fault tolerance in comparison to [2][3]. In high voltage mode, the fault tolerant mechanism of RDC-Cache is turned-off with minimal (0.91%) latency overhead compared to a traditional cache. Copyright 2009 ACM.