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I noticed a NIC from Realtek has an option to "offload" some of the CPU work for checksums onto itself. However, this has some - I would say - humorous effects on opinions of people on the web: Some say it is a performance increase for multimedia applications (i.e. games), while others say by removing that option and letting the CPU do it is an increase.

Assume the machine is multi-processor and the multimedia application is not fully multi-threaded; will a NIC offer lower latency by offloading checksum work or will the CPU doing it (on a non-congested processor) be better?

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Im not an expert in this but if a device such has a NIC says it can do the calculation internally without the need of the CPU then its got to be faster as it would have its own chip to do the calculation and that chip would be specificity designed to do the maths rather than offloading it to the CPU.

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At least that's the theory. –  mtone Dec 23 '11 at 15:50

In your scenario: It doesn't matter.

In higher end scenarios: A customized ASIC (or a good FPGA) are designed to enhance performance, but will handle more than simple packet checksums -- high end server NICs will Offload all TCP/IP processing from the rest of the system. When you're talking about a multi-port Gigabit Ethernet (or 10 GbE!) card that's a lot of processing that's taken off of the CPU.

It doesn't matter for you because the checksum calculcation is pretty trivial and takes next to zero time on any modern system or NIC anyway, and your internet connection is almost certainly going to be the single contributing factor (in a non-broken network) when it comes to latency and bandwidth.

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