SFFMap: Set-First Fill mapping for an energy efficient pipelined data cache

Conventionally, consecutively addressed blocks are mapped onto different sets in cache. In this work, we propose a new block address mapping, Set-First Fill (SFFMap), for pipelined L1 data caches wherein consecutively addressed data blocks are mapped onto the same set. This increases the inter-block spatial locality within the cache set. In order to exploit SFFMap, we propose to store and if possible, access the most recently used set in the cache's pipeline registers. Further, selective access (SSA) and selective update (SSU) techniques are proposed for set-buffer to increase the effectiveness of SFFMap. Our experimental evaluation for in-order and out-of-order processors with an 8-way set-associative data cache shows that SFFMap, together with SSA and SSU, achieves around 27% reduction in dynamic energy and 4-5% performance improvement. The proposed techniques need minor modifications to the existing hardware, making it an adoptable design.