What's the Actual Speed in GHz of RapidIO or RocketIO serial interfaces?
RapidIO employs one or more LVDS (low voltage differential signal) lanes in parallel.

The Unit Interval (simply the duration of one bit) of each single lane is 320 ps (equals 3.125 GHz) when transmitting at 3.125 Gbaud. 

It is square-waved, with defined rise and fall times of the signal. 

Read more at chapter 8 of http://www.rapidio.org/data/specs/SerialSpec_v_1pt2.pdf