1. A method comprising: a. sampling a first series of input symbols using a first voltage threshold to produce a series of first sampled symbols, wherein each of the first sampled symbols represents one of a plurality of logic levels, including a first logic level and a second logic level; b. calculating a first probability that the first sampled symbols represent the first logic level; c. sampling a second series of input symbols using a second voltage threshold to produce a series of second sampled symbols, wherein each of the second sampled symbols represents one of the plurality of logic levels, including the first logic level and the second logic level; and d. calculating a second probability that the second sampled symbols represent the first logic level.