Why is Core 2 Duo prefered for chess programming?

[bob]

A single core-2 processor (just one CPU) is more than twice as fast as a single PIV 2.8ghz xeon. My office machine using both cpus hits 1.5-2.0M nps. My 2.0ghz core-2 laptop hits 5-6M nps.

the comparison is startling...

Note that the xeon box in my office is 32 bit, while my core-2 is 64 bit and I'm running 64 bit linux (suse 10.2)...

Umm... forgive me if I'm missing something, but isn't it obvious that the 64-bit factor plays a role? Or is that exactly the point you were making?

Yep. The whole "package" is way faster. But even if the application was not compiled for 64 bits, it is way faster on the core-2 than on the PIV by a factor of 2x.

[sje]

Another issue to consider, if you're an author, is the effect on development time. I've found that compilation is much faster with dual and quad core machines in those cases where the development environment supports multiple simultaneous compilation threads.

For example, the Xcode IDE running on a Macintosh in distributed compilation mode starts up two g++ threads per core. The setup can do in a single minute on a quad core Xeon what would take eight minutes on a 3 GHz Pentium 4 and more than half an hour on a 400 MHz PowerPC.