Turbocharge Your TP-Link TL-WR840N (ME) V6.20 : The Ultimate Firmware Guide

A small but significant feature in this firmware iteration was the improvement of the bridging function. Users in large homes would often buy two WR840Ns to link them wirelessly and cover a dead zone. Previous firmware versions were finicky with this; 6.20 smoothed out the handshake protocol, making the bridge more resilient to signal drops.

The 6.20 firmware is a testament to the idea that you don't need to be the fastest to be essential; you just need to work, every time, without asking for thanks.