OK, here's the edges from a very simple pulse generator:
- the source is 5V with no load, but obviously it is used to drive 2.5V into the scopes' 50ohm input
- 4GHz LeCroy HDO4904, connected directly to the scope input with a BNCfemale-BNCfemale adaptor
- 1GHz Agilent MSOS104A, connected via a 1m piece of coax of untested quality
It looks like the 10%-90% risetime is 256ps with a 6.3% overshoot, and the falltime is 453ps with a 3.8% overshoot.
Considering the simplicity of the circuit, that is remarkably fast. It is a simple demonstration that modern jellybean logic (74LVC1G*) generates significant power into the microwave waveband - and hence RF practices are appropriate.
In this circuit a major contributor to the performance is the decoupling capactors, especially the 0V/5V planes and short wide wires, and not forgetting that MLCCs have a very significantly reduced capacitance when there's a DC bias voltage.
My apologies for the quality of the photos; they had to be taken relatively quickly and in non-ideal conditions.