Originally Posted by debian_penguin
xorbe: is kwrite the only app causing your cpu go skyrocketing, or is it a general kde problem?
'cause I had a similar problem with all kwrite-based applications (kate, kdevelop, kile...), and it turned out to be a problem completely unrelated to rendering (though it looked like it: scrolling is really slow, letters apprear much slower than they are typed...). It's a bug of some sort in the undo cache generation and management. I solved it by telling applications to keep trace of about 400 undoings rather than an unlimited number of those.
Well, I apologize if it is not your case
just my two cents,
I just tried this, it didn't solve the issue here. Worth a shot, though.