DRAM row buffer conflicts can increase the memory access latency significantly for single-threaded applications. In a chip multiprocessor system, multiple applications competing for DRAM will suffer additional row buffer conflicts due to interthread interference. This paper presents a new hardware and software cooperative DRAM bank partitioning method that combines page coloring and XOR cache mapping to evaluate the benefit potential of reducing interthread interference. Using SPECfp2000 as our benchmarks, our simulation results show that our scheme can boost the performance of the most benchmark combinations tested, with the speedups of up to 13%, 14% and 8.06% observed for two cores (with 16 banks), two cores (with 32 banks) and four cores (with 32 banks).