A Variable Bitline Data Cache for low power design

Reducing the power consumption is one of the most important design problems at present. Modern microprocessors employ caches to bridge the great speed variance between the main memory and the central processing unit, but these caches propose larger and larger proportion in the total power consumption. In fact, many values rarely need the full-bit dynamic range supported by a cache. The Narrow-Width Value (NWV) occupies a large portion of cache access and storage. It is unreasonable that the storage space for value of any data width is the same in the cache, even if NWV needs only a few bits to be stored. This paper proposes a Variable Bitline Data Cache (VBDC) which exploits the popularity of NWV stored in the cache. In VBDC design, the cache data array is divided into several sub-arrays to adapt each data pattern with the different bitline length to access. The VBDC can shut off the corresponding unused high arrays to reduce its dynamic and static power consumption. The VBDC achieves low power consumption through reducing the bitline length. Experimental results employing SPEC 2000 benchmarks show that our proposed VBDC can reduce both the dynamic power consumption ant the static power consumption by 44.75% and 42.86%.