Comment 12 for bug 297143

I can confirm. My university's wireless is horrible sometimes, and this is the observed behavior.
At first, I thought it was because I was using a softmac wireless card, but a quick look at top shows Xorg being the one hogging cycles. This problem is even worse when using a compositor.
And of course, this effects all gecko related projects; thunderbird, firefox, seamonkey, etc.
Recent trunk builds exhibit the same effect.

My best guess is that gecko tries to rerender the client display every time it gets new data. As the connection is slow/unstable, data comes in at a trickle, leading it to make a lot of X calls to redraw the client. Turning off whatever loading animations I could and lowering the page redraw frequency alleviated the situation somewhat.