Well you can't say exactly that you want it to only use 8% of the processor, but you could set the update rate to like 5 per second max and probably get around 8% or less.
Radmin isn't that cpu intensive, but one of the things I like most about it is that I can tell it to use as much of the processor as possible, which gives great performance. Other programs just assume they're not supposed to use the processor very much.