propabad and apparatus for reducing memory requirements and increasing speed of decoding of turbo encoded data in a MAP decoder. Turbo coded data is decoded by computing alpha values and saving checkpoint alpha values on a stack. The checkpoint values are then used to recreate the alpha values to be used in computations when needed. By saving only a subset of the Alpha values memory to hold them is conserved. Alpha and beta computations are made using a min* operation which provides a mathematic equivalence for adding logarithmic values without having to convert from the logarithmic domain. To increase the speed of the min* operation logarithmic values are computed assuming that one min* input is larger than the other and visa versa at the same time. The correct value is selected later based on a partial resulta calculation comparing the values accepted for the min* calculation. Additionally calculations are begun without waiting for previous calculations to finish. The computational values are kept to a minimal accuracy to minimize propagation delay. An offset is added to the logarithmic calculations in order to keep the calculations from becoming negative and requiring another bit to represent a sign bit. Circuits that correct for errors in partial results are employed. Normalization circuits which zero alpha and beta most significant bits based on a previous decoder interation are employed to add only minimal time to circuit critical paths.