Connect your Atom board to the D-Link router (disable the pppoe stuff) and from the command line, download by ftp a big file.
Jot down the speed. Then change the tcp receive speed like in my post and redownload it. See if the download speed approaches the one from your laptop directly connected to the D-link router.
A simple way to download a big file:
Code:
$ ftp -4a ftp://ftp.openbsd.org/pub/OpenBSD/4.6/i386/base46.tgz
Because
ftp.openbsd.org can be busy at times, you better select a mirror close by. The file path usually is the same, see
http://www.openbsd.org/ftp.html