8. An apparatus comprising: an interface device configured to: receive Hidden Markov Model (HMM) information from an external processing unit, wherein the external processing unit is configured to receive speech from a user and further configured to process the speech via an acoustic modeling process and a phoneme evaluation process, wherein the HMM information is derived from a plurality of HMMs, each HMM having a different type of data structure, and wherein the different structures comprise Ergodic HMM structures, left-to-right structures, and parallel path left-to-right HMM structures; and format the HMM information from each of the plurality of HMMs into a common HMM data structure to access the HMM information based on a priori knowledge of one or more fields and one or more indices in the common HMM data structure wherein the formatting comprises formatting HMM information from at least one of a plurality of fields of the plurality of HMMs into the common HMM data structure; a processing device comprising: a state type fetch module configured to determine a presence of one or more NULL and non-NULL states in the common HMM data structure, each NULL state being a non-emitting state identified by a state-type flag; a processing module configured to: process back pointer data and first HMM state scores for the one or more NULL states; after back pointer data and first HMM state scores have been processed for each of the one or more NULL states, process second HMM state scores for one or more non-NULL states based on at least one predecessor state; an output list module configured to transfer the second HMM state scores to the external processing unit, wherein the external processing unit outputs decoded speech based on the second HMM state scores; and a memory device configured to store the HMM information.
14. The apparatus of claim 8 , wherein the processing module is configured to select a maximum value associated with one or more predecessor states, wherein the maximum value is based on a state score and a transition probability associated with the one or more predecessor states.