Feedback Cache Mechanism for Dynamically Reconfigurable VLIW Processors

Very Long Instruction Word （VLIW） architectures are commonly used in application-specific domains due to their parallelism and low-power characteristics. Recently, parameterization of such architectures allows for runtime adaptation of the issue-width to match the inherent Instruction Level Parallelism （ILP） of an application. One implementation of such an approach is that the event of the issue-width switching dynamically triggers the reconfiguration of the data cache at runtime. In this paper, the relationship between cache resizing and issue-width is well investigated. We have observed that the requirement of the cache does not always correlate with the issue- width of the VLIW processor. To further coordinate the cache resizing with the changing issue-width, we present a novel feedback mechanism to ＂block＂ the low yields of cache resizing when the issue-width changes. In this manner, our feedback cache mechanism has a coordinated effort with the issue-width changes, which leads to a noticeable improvement of the cache performance. The experiments show that there is 10% energy savings as well as a 2.3% cache misses decline on average achieved, compared with the cache without the feedback mechanism. Therefore, the feedback mechanism is proven to have the capability to ensure more benefits are achieved from the dynamic and frequent reconfiguration.