The next benchmark is run with the optimization flags:

Finally, we have the architecture optimized flags as well:

You are reading these charts correctly, the O3 flag actually penalizes the AMD CPU.  We also compiled the program with -O2 -march=k8 but we got virtually the same score with or without the march flag.

We were informed others have been capable of much faster nodes per second using GCC 3.4.1 and the flagset:

We did not have time to fully test GCC 3.4.1, although there is a strong likelihood that 3.4 encourages better optimizations (particularly on the x86_64 platforms).

Crafty

For good measure, we have included Crafty into our chess benchmarks section.  Crafty was only built using the "make linux-amd64" target.  From the Makefile, it seems as though the "AMD64" moniker is slightly inappropriate.  The target claims:

The benchmark was generated by running the "bench" command inside the program.

It is clear the difference between both processors is quite severe in this instance.  Although it is difficult to pin an exact culprit, there are likely multiple arch optimizations were left untapped, and thus our reasoning for discouraging overusage of optimizations in general.