The quad data rate trick is reading on differentiated and level gated clock. Actual clock signal is still same rate. Works when clock rates are high as the tran

The quad data rate trick is reading on differentiated and level gated clock. Actual clock signal is still same rate. Works when clock rates are high as the transition time gets close to clock pulse time - the clock is no longer considered square but exponential trapezoid. It is 2x bandwidth compared to just using clock edges, but requires nice bypassing to get nice clock transitions and is obviously quite a bit higher transistor count for stabilization. It is similar to clock doubling but much simpler and thus faster. Of course you get some latency benefit.