Intel Pentium 4 1.7GHz: Does the prophecy hold true?

Memory Bandwidth Comparison

Again you see that the Pentium 4 can truly make use of RDRAM while the Pentium III had very little use for that type of bandwidth.  The first thing to notice here is that both setups advertise considerably higher memory bandwidth figures than are actually being delivered here, and Cachemem isn’t even a real world use benchmark. 

The dual channel PC800 RDRAM setup of the Pentium 4 promises up to 3.2GB/s of memory bandwidth and delivers half of that.  The Athlon’s PC2100 DDR SDRAM promises 2.1GB/s and provides about 52% of that as well.

There is nothing too surprising here; we have always known the Pentium 4’s platform to have much more memory bandwidth than any competing solution. 

To conclude our bandwidth measurements we have the trusty Linpack benchmark.  As you’ll know, the first half of the graph is determined mainly by cache performance and thus clock speed (because in both of these cases the L2 cache operates at the clock frequency).  However we don’t want you comparing clock speeds since we’ve already been through the differences in the architecture, rather we want you to look at the differences in the behaviors of the architectures. 

Notice first of all that in spite of the clock speed advantage, the Pentium 4 does not offer a bandwidth improvement over the Athlon for the first 128KB.  This just goes to show you that clock speed doesn’t mean everything, and a clock for clock comparison between the Pentium 4 and the Athlon is not as useful as it was with the Pentium III since the P3 was much more similar to the Athlon in terms of pipeline length. 

There is a small portion of the graph, while both processors are still dealing with data in their caches, that the Pentium 4 holds a performance advantage over the Athlon.  This advantage is most likely due to the higher bandwidth L2 cache subsystem but what is interesting is that the performance advantage only occurs in a very small portion of the graph, indicating that AMD’s 64-bit L2 cache bus may not be all that horrible for its performance.

The latter half of the graph is governed entirely by main memory bandwidth and isn’t affected by CPU performance as much.  Here you can see RDRAM’s bandwidth advantage over DDR SDRAM in a different light.

Now that we’ve seen the latency and bandwidth differences between the fastest processors from both camps, let’s step into the ring and see how these fighters do in the real world.