[adam_walker]

Yes, this is about building a small hashtable in the RAMs internal to the FPGA. As you pointed out, things would slow down a bit if you had to go to external RAM.

However, if you are building a hashtable in external RAM that is accessed via Ethernet, I think there are still some performance gains to be had with an FPGA compared to a non-specialized device.

For one, you get to skip the PCIe bus with an FPGA, reducing latency, since the Ethernet transceivers go straight into the FPGA fabric. Also, while I don't know a lot about power consumption, I expect it would be a fair bit lower on a dedicated FPGA compared to a server performing the same work.