Inspired by this question:

How do I calculate clock speed in multi-core processors?

The answers in the above question do a fair job of explaining why a lower-speed multi-core processor won't necessarily perform at the same level as a higher-speed single-core processor.

Example: 4*2=8, but a quad-core 2 GHz processor isn't necessarily as fast as a single-core 8 GHz processor.

However, I'm having a hard time putting the information in those answers to practical use in my mind. Particularly, I want to know how it should be used to judge whether a given CPU is appropriate for an application with specific requirements.

Example scenarios:

• An application has a minimum CPU requirement of 2.4 GHz dual-core.
• Another application has a minimum CPU requirement of 1.8 GHz single-core.

For either of the above scenarios: Would a higher-speed processor with fewer cores, or a lower-speed processor with more cores, be equally sufficient? If so, how can we determine the appropriate processor speeds required for a given number of cores?