Signal Quality

Data transfer requires the clean reception of data signals and clock signals. Ringing below receiver thresholds, non-monotonic signal edges, and excessive voltage swings will adversely affect system timings. Ringback and signal non-monotonicity cannot be tolerated since these phenomena may inadvertently advance receiver state machines. Excessive signal swings (overshoot and undershoot) are detrimental to silicon gate oxide integrity, and can cause device failure if absolute voltage limits are exceeded.

Overshoot and undershoot can also cause timing degradation due to the build up of Inter-Symbol Interference (ISI) effects.

For these reasons, it is crucial that the designer work towards a solution that provides acceptable signal quality across all systematic variations encountered in volume manufacturing.

This section documents signal quality metrics used to derive topology and routing guidelines through simulation. All specifications are specified at the processor die (pad measurements).

Specifications for signal quality are for measurements at the processor core only and are only observable through simulation. Therefore, proper simulation is the only way to verify proper timing and signal quality.