Practical ways to associate a known pulse to an adequate oscilloscope bandwidth
Square waves are composed of higher-order harmonics of the fundamental rep rate. The faster the transition time (that is, rise/fall time), the more harmonics you need to get to give a usable picture of the wave. So it’s more about that than the actual clock frequency.
More here: https://www.fluke.com/en-us/learn/blog/oscilloscopes/what-is-the-relationship-between-oscilloscope-bandwidth-and-waveform-rise-time
The article uses the following relation:

Bandwidth = 0.35 / risetime(s)

So for that 1ns pulse, assuming a risetime of say, 300ps, we get 1.16 GHz as the required bandwidth.