You have been asked to investigate the relative performance of a banked versus pipelined L1 data cache for a new microprocessor. Assume a 64 KB two-way set associative cache with 64-byte blocks. The pipelined cache would consist of three pipe stages, similar in capacity to the Alpha 21264 data cache. A banked implementation would consist of two 32 KB two-way set associative banks. Use CACTI and assume a 65 nm (0.065 m) technology to answer the following questions. The cycle time output in the web version shows at what frequency a cache can operate without any bubbles in the pipeline.
Find the average memory access time if 20% of the cache access pipe stages are empty due to data dependencies introduced by pipelining the cache and pipelining more finely double the miss penalty. The access time is 0.92ns, the cycle time is 0.3ns. The number of pipeline stages is 3 and the miss rate is 0.0036.

When making changes to optimize part of a processor, it is often the case that speeding up one type of instruction comes at the cost of slowing down something else. for example, if we put in a complicated fast floating-point unit, that takes space, and something might have to be moved farther away from the middle to accommodate it, adding an extra cycle in delay to reach that unit. the basic amdahl's law equation does not take into account this trade-off. a. if the new fast floating-point unit speeds up floating-point operations by, on average, 2ă—, and floating-point operations take 20% of the original program's execution time, what is the overall speedup (ignoring the penalty to any other instructions)? b. now assume that speeding up the floating-point unit slowed down data cache accesses, resulting in a 1.5ă— slowdown (or 2/3 speedup). data cache accesses consume 10% of the execution time. what is the overall speedup now? c. after implementing the new floating-point operations, what percentage of execution time is spent on floating-point operations? what percentage is spent on data cache accesses?