Why does the speed on the router sag?

Question

TP Link

There is a Tp-link 741nd router, speed subsidence was noticed on it, through pppoe, it does not rise above 700 kb / s. But sometimes the speed rises to logical 100 mb over the wire. Hardware version 4.2, tried openwrt 12.09, 14.07 and standard, the problem is about the same everywhere. The Asus n10+ standing next to it gives out the maximum 3 MB / s for it. Where to dig?

Answer 1

The same situation was observed by my friend
in one direction above 380 kb does not rise
in the other direction 1 gigabit per second
Tp-Link router after the
tests found out that there was a problem with the computer search until windows 10 upgrade