Systems of screening memory cells of a memory include modulating bitline and/or wordline voltage. In a read operation, the wordline may be overdriven or underdriven with respect to a nominal operating voltage on the wordline. In a write operation, one or both of the bitline and wordline may be overdriven or underdriven with respect to corresponding a nominal operating voltage. Such a system has margin control circuity, which may be in the form of bitline and wordline margin controls, to modulate bitline and wordline voltages, respectively, in the memory cells of the memory array.