When the new content is added to the SharePoint Farm 2010 the indexing is starting. The feed performance is mainly determined by the configured number of item processing components. Both the number of the CPU cores and the speed of each of them affects the results.
As a first order approximation, a 1 GHz CPU core can process one average size (about 250 KB) Office document per second. For example, total estimated throughput of the Server with 48 CPU cores for item processing, each being 2.26 GHz, is 48 cores × 2.26 GHz ≈ 100 items per second, on average.