Lag when I turn the monitor 90 degrees

[jmsgm_dl]

I recently bought a club3d adapter to connect a small monitor (17 inch 1280x1024) to my macbook pro 2010 (10.9 Mavericks).

In its standard rotation it works perfectly, but when I turn it 90 it starts to have a lot of lag. It does not make sense because the resolution is the same.

The installed version is DisplayLink 75598 this is the last?

What is the problem? Thank you.