Assume that the number of accessible CPU cores doubles every 18 months. How much more off-chip memory bandwidth would a CPU launched in three years need to maintain the same per-core performance?

Suppose that every 18 months, new generations of CPUs add another core to the number that can be used. Three years from now, how much extra off-chip memory bandwidth will be needed for a CPU to keep up with the same level of per-core speed?

Consider a virtual memory system with the following characteristics for accessing memory: 1 nanosecond for a read operation with a hit in cache 5 nanoseconds for a read operation with a miss in cache 2 nanoseconds for a write operation with a hit in cache 10 nanoseconds for a write operation with a miss in cache The cache hit ratio is 0.9   If a sequence of instructions were executed: 100 instruction fetch operations, 60 memory operand read operations, and 40 memory operand write operations, what would be the average memory access time (in nanoseconds) in executing the sequence of instructions:

Assume new CPUs double cores every 18 months. How much off-chip memory bandwidth would a CPU released in three years need to maintain per-core performance?