How to compare CPUs?
I am not sure what you mean with task specific performance, so you will get a slightly generic answer.
There are a lot of different metrics for comparing CPU's, and it depends a lot on what you intend to do with them. The most common meta statistics are:
- Performance/price
- Performance/watt
And the ever popular weighted index such as
- Performance/(price + watt*3 years of electricity)
Performance in turn can be measured in many ways:
- MHz (oooh! Marketing!)
- Synthetic benchmarks
- Memory bandwith (Often the limit in HPC applications)
- Application performance for a specific application
You should compare the CPU performance against the intended application. If your application is a virtualization server with 200 virtual hosts you will want a very different CPU from what you need in a mobile phone or in a firewall. Outside the HPC world it's rare that a single test captures most of the performance characteristics you are interested in.
Usually SpecInt 2006 (http://www.spec.org/cpu2006/CINT2006/) are a good start.