and a second trace 160 first trace 154 is located on a lower high speed layer and connects to two thru holes 152 and 156 second trace 160 is located on an upper high speed layer and connects to two thru holes 158 and 162 a signal launched into thru hole 152 travels down trace 154 but also travels down the remainder of thru hole 152 which forms a stub 164 that reflects the signal back in the other direction likewise a signal launched into thru hole 158 travels down trace 160 but also travels down the remainder of thru hole 158 which forms a much longer stub 166 that reflects the signal back in the other direction similar reflections occur at the exit ends of traces 154 and 160 longer stub 166 produces a much more problematic reflection than shorter stub 164 one way that this tendency is compensated for in the preferred embodiments is by routing shorter traces on the upper high speed layers where the reflections are more significant but the signal is not as degraded due to a long propagation path and routing longer traces on the lower high speed layers where the reflections are less significant and thus longer path lengths with more attenuation can be tolerated in conjunction with the goal of dividing traces by dedicating high speed layers.