An apparatus comprising: N conductors configured to receive N symbols corresponding to a codeword, wherein N is an integer greater than 2, and wherein the N conductors are subdivided into at least two groups of conductors, each group comprising one or more conductors; and a sparse comparator unit connected to the N conductors, the SCU comprising M two-input comparators configured to generate M comparator outputs that map directly to K output bits, where M < N ∗ (N-1)/2, and where K ≤ M, the SCU comprising: one or more local SCUs, each local SCU comprising one or more two-input comparators of the M two-input comparators, wherein each local SCU accepts a respective group of conductors of the at least two subdivided groups of conductors as inputs, each local SCU having one or more fine codeword comparator outputs representing comparisons of symbols received on the group of conductors; an arithmetic unit comprising at least one averaging unit connected to a first group of conductors of the at least two subdivided groups of conductors, and generating an output that represents an average of signals on the first group of conductors; and, a global comparator unit comprising at least one two-input comparator of the M two-input comparators connected to (i) the output of the at least one averaging unit and (ii) a conductor in a second group of conductors of the at least two subdivided groups of conductors or an output of a second averaging unit connected to conductors of the second group, the at least one two-input comparator providing a coarse codeword comparator output composed of a set of one or more coarse codeword comparator outputs, wherein a data word corresponding to the codeword is determined based on the sets of fine codeword comparator outputs and the one or more coarse codeword comparator outputs. N conductors configured to receive N symbols corresponding to a codeword, wherein N is an integer greater than 2, and wherein the N conductors are subdivided into at least two groups of conductors, each group comprising one or more conductors; and a sparse comparator unit connected to the N conductors, the SCU comprising M two-input comparators configured to generate M comparator outputs that map directly to K output bits, where M < N ∗ (N-1)/2, and where K ≤ M, the SCU comprising: one or more local SCUs, each local SCU comprising one or more two-input comparators of the M two-input comparators, wherein each local SCU accepts a respective group of conductors of the at least two subdivided groups of conductors as inputs, each local SCU having one or more fine codeword comparator outputs representing comparisons of symbols received on the group of conductors; an arithmetic unit comprising at least one averaging unit connected to a first group of conductors of the at least two subdivided groups of conductors, and generating an output that represents an average of signals on the first group of conductors; and, a global comparator unit comprising at least one two-input comparator of the M two-input comparators connected to (i) the output of the at least one averaging unit and (ii) a conductor in a second group of conductors of the at least two subdivided groups of conductors or an output of a second averaging unit connected to conductors of the second group, the at least one two-input comparator providing a coarse codeword comparator output composed of a set of one or more coarse codeword comparator outputs, one or more local SCUs, each local SCU comprising one or more two-input comparators of the M two-input comparators, wherein each local SCU accepts a respective group of conductors of the at least two subdivided groups of conductors as inputs, each local SCU having one or more fine codeword comparator outputs representing comparisons of symbols received on the group of conductors; an arithmetic unit comprising at least one averaging unit connected to a first group of conductors of the at least two subdivided groups of conductors, and generating an output that represents an average of signals on the first group of conductors; and, a global comparator unit comprising at least one two-input comparator of the M two-input comparators connected to (i) the output of the at least one averaging unit and (ii) a conductor in a second group of conductors of the at least two subdivided groups of conductors or an output of a second averaging unit connected to conductors of the second group, the at least one two-input comparator providing a coarse codeword comparator output composed of a set of one or more coarse codeword comparator outputs, wherein a data word corresponding to the codeword is determined based on the sets of fine codeword comparator outputs and the one or more coarse codeword comparator outputs.