Hardware/Software managed scratchpad memory for embedded systems

Abstract

In this paper, we propose a methodology for energy reduction and performance improvement. The target system comprises of an instruction scratchpad memory instead of an instruction cache. Highly utilized code segments are copied into the scratchpad memory, and are executed from the scratchpad. The copying of code segments from main memory tu the scratchpad is performed during runtime. A custom hardware controller is used to manage the copying process. The hardware controller is activated by strategically placed custom instructions within the executing program. These custom instructions inform the hardware controller when to copy during program execution. Novel heuristic algorithms are implemented to determine locations within the program tu insert these custom instructions, as well as tu chwse the best sets of code segments to he copied tu the scratchpad memory. For a set of realistic benchmarks, experimental results indicate the method uses 50.7% lower energy (on average) and improves performance by 53.2% (on average) when compared tu a traditional cache system which is identical in size. Cache systems compared had sizes ranging from 256 to 16K bytes and associativities ranging from 1 tu 32.