"PCI-Express just great for 1Gbps / embedded in ICH8 Gigabit adapter 82566DC, have because of bug, or by design internal FIFO only 16K! It's means 8K for RX, and 8K for TX / Because of small FIFO buffer and probably PCI-Express latency, on high packet-rate (around 100Kpps) you will hit a wall. "
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https://nuclearcat.com/mediawiki/index.php/Intel_Gigabit_Performance
