"Here is where threading helps a lot. If you have a cache miss and are facing a long wait for something to come back from memory, you just switch to another thread. That thread can execute its instruction stream until it hits a pothole, then it hands execution off to another thread. Intel has the ability to do this between two threads on the Pentium 4 with hyperthreading, and Niagara has four threads running in parallel per core. To make up numbers, if a cache miss takes 100 cycles, and on average each thread can execute for 25 cycles before it needs to hit main memory, in theory you should completely hide memory latency."
(Submitted by Noel Mon Nov 8, 2004 )
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