You might be selling general purpose CPUs short. To me the computing hardly seems like the daunting part, it's the IO (both the wire interface, and all the inte

You might be selling general purpose CPUs short. To me the computing hardly seems like the daunting part, it's the IO (both the wire interface, and all the internal buses). To verify that intuition, I just did a quick experiment with an Intel 10Gbps NIC and a Xeon E5506. The workload was roughly similar to switching: read packet, parse the headers, extract some fields from the headers and use that as a key to a hash table lookup, write packet out to a different interface. This was done using code from a much more complicated system that I didn't spend any time tuning for just this case, so it's absurdly wasteful (e.g. spending 10% of the runtime just on useless calls to RDTSC). The result was 4.3 Mpps, or about 500 cycles / packet. That seems far from 83 Mpps / 42 cycles, but it was using a single core and a single rx queue on the NIC. Make it parallel with 16 cores / queues, and you're in the right ballpark. And then remember that we're talking of a 3.5 year old CPU, which was already low end when it launched.