Another example: PCIe ASPM exit latency. Fast LAN speed (because the card does not have time to go into sleep) but low internet speed (manages to enter ASPM if the host is at least 3ms away)

https://lore.kernel.org/intel-wired-lan/803760bf-04ff-4b23-8...

good old buffer packet size

anyone old enough from dialup modems and RS232 to remember the trick of replacing the 16450 UART with 16550 if you were lucky enough to have it on a socket instead of soldered?

that took it from a 1-byte buffer to 16-bytes, instant speed boost

same idea going from X-modem to Y-modem for transfers, 128bytes vs 1024bytes before checksum

surprised ethernet by now doesn't constantly try to negotiate larger buffer windows