A memory chip having a data bus having a plurality of bits. The number of bits is apportioned between a read portion and a write portion. The write portion is dedicated to receiving data that is to be written into an array on the memory chip; the read portion is dedicated to driving data that has been read from the array on the memory chip. The apportionment is programmable. Apportionment can be specified by programming signal pins on the memory chip, connecting the signal pins to appropriate logical values. The apportionment can alternatively be specified by scanning apportionment information into the memory chip at bring up time. The apportionment and also alternatively be specified by receiving apportionment information in an address/command word.