The Virtual Open Page Buffer for Multi-core and Multi-thread Processors

The performance of off-chip DDRx SDRAM has been greatly restricted by the single physical page that can be activated for each DRAM bank at any time. To alleviate this problem, an on-chip virtual open page buffer (VOPB) for multi-core multi-thread processor is proposed. The VOPB maintains a number of virtual active pages for each bank of off-chip memory, which effectively increases the maximum number of active pages and reduces page conflicts in the off-chip memory. Adopted by the FT-1500 processor, the VOPB along with optimized address mapping techniques greatly enhances the bandwidth, latency and energy efficiency of off-chip memory, especially for stream applications. Experimental results show that the VOPB improves off-chip memory bandwidth by 16.87% for Stream OpenMP and 6% for NPB-MPI on average.