Similarly, it must not stall the cache on a miss caused by a speculative instruction. Data in a writeback cache is not written to memory immediately so memory has stale data. This eliminates the consistency problem. The drawback is that the checking slows down the cache. Fallacies and Pitfalls Don't predict cache performance of program A from program B .
Programs vary widely in how they use cache.
A scientific program may have a small tight code loop but access large quantities of data. On the other hand, a word processing program might operate on relatively little data but use lots of code. Simulate plenty of memory references . A CPU executes 100 million or more instructions per second. Simulating cache behavior using traces of only a few million traces can be misleading.