It's been a while since I looked at high speed scopes. But last I heard, they were topping out around 5Gsamples/sec for a very expensive tek. Now I see ads in microwave magazines for scopes that claim sampling rates of up to 100GHz. I don't know anyone who makes an A/D chip that will sample at anything close to 100GHz or a memory manufacturer who can handle that kind of data rate. So what's the trick? Are they ping-ponging a large bank of slower A/D's ? Does the enormous sample rate only apply to repetitive waveforms? Or can I really put a single 100psec pulse into these things and get 10 clean points on it?