If you have enough disk bandwidth and no other bottlenecks, then Oracle will be able to use all your CPU capacity regardless of the number of CPUs and their speed. However, all other things being equal, a smaller number of faster CPUs will outperform a larger number of slower CPUs because of the relative impact of the hardware's cache coherency mechanism.

However, if your long-running reports tend to be I/O bound (as is normal) then you may be better advised to choose the cheaper rather than better CPU configuration, so as to devote as much of your budget as possible to I/O bandwidth.

We are in the process of selecting Sun machines for Oracle database, for example E6500 or E10K. If our budget is fixed, which kind of configuration will be better for Oracle: more CPUs or more MHz? Normally, what is the optimal number of CPUs Oracle parallel processes utilize?

If the biggest problem of our Oracle application is long-running reporting queries, which kind of configuration is better?