Topic: FPS drops/slowdown while harvesting

Best illustrated as:

http://i.imgur.com/YDAPI.png

Whenever I activate a bunch of harvesters, the CPU usage of the client jumps. With a single client running, the slowdown means a couple of frames, but with two clients, even my keyboard start getting ignored (within the client).

This is also shown on the image linked. I haven't encountered it with anything else yet though, just harvesting.

My hardware is somewhat outdated, but not old enough for Perpetuum. Think Core 2 Duo E6850, 4GB of RAM and an HD6870.