In reviewing CPU and server benchmarks, you’ve undoubtedly noticed that testing covers both single-core and multi-core performance. Here’s the difference.
In terms of raw performance, both are equally important, but single- and multi-core have areas of use where they shine. So when picking a CPU, it’s important to consider your particular workloads and evaluate whether single-core or multi-core best meets your needs.
There are still a lot of applications out there that are single-core limited, such as many databases (although some, like MySQL, are multicore).
Performance is measured in a couple of ways. Clock frequency is the big one; the higher the frequency the faster apps will run. Also important is the width of execution pipelines, and the wider the pipeline, the more work can get done per clock cycle. So even if an app is single threaded, a wider pipeline can improve its performance.
Source:: Network World – Data Center