The Athlon isn’t the Pentium 4

The Pentium 4 architecture in particular was designed around the assumption that the processor would have a considerable amount of memory bandwidth at its disposal.  We proved this in our Pentium 4 Review without having the necessary data to support it through our Linpack tests.  Let’s have a quick refresher on what we noticed about the Pentium 4’s Linpack performance with its dual channel PC800 RDRAM (3.2GB/s bandwidth). 

As you can see from the above graph, once the test data gets too big to fit within the L2 caches of the processors the Linpack performance is determined directly by the performance of the memory subsystem. 

However the problem we had in our original Pentium 4 Review when analyzing these results was that the Pentium 4 used the same memory subsystem as the Pentium III on the i840, yet the Pentium 4 was almost 2.5 times faster than the Pentium III on the i840, yet they shared the same exact memory subsystem (dual channel PC800 RDRAM).  Without any PC600 RDRAM to confirm the Pentium 4’s memory bandwidth dependency, we couldn’t rule that it was the i850’s dual channel RDRAM that was helping the Pentium 4 there.

Shortly thereafter, we got our hands on some PC600 RDRAM and repeated the same test, this time the Pentium 4 had only 66% of the memory bandwidth that was available during the first time we benchmarked it. 

Index The Athlon isn't Memory Bandwidth Hungry
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