Question

Assume that a DDR2-667 2 GB DIMM with CL = 5 (CL is the Column Address Strobe Length in clocks) is available for $130 and a DDR2-533 2 GB DIMM with CL = 4 is available for $100. Assume that two DIMMs are used in a system, and the rest of the system costs $800. Consider the performance of the system using the DDR2-667 and DDR2-533 DIMMs on a workload with 3.33 L2 misses per 1K instructions, and assume that 80% of all DRAM reads require an activate.  For DDR2-667, the latencies to service an L-2 miss are 14 cycles and 9 cycles for reads requiring activate, and for reads not requiring activate, respectively. For DDR2-533, the latencies to service an L-2 miss are 12 cycles and 8 cycles for reads requiring activate, and for reads not requiring activate, respectively.  What is the cost-performance of the entire system when using the different DIMMs, assuming only one L2 miss is outstanding at a time and an in-order core with a CPI of 1.5 not including L2 cache miss memory access time?

Answer 1