An integrated-circuit memory controller outputs to a memory device a first signal in a first state to enable operation of synchronous data transmission and reception circuits within the memory device. A transaction queue within the memory controller stores memory read and write requests that, to be serviced, require operation of the synchronous data transmission and reception circuits, respectively, within the memory device. Power control circuitry within the memory controller determines that the transaction queue has reached a predetermined state and, in response, outputs the first signal to the memory device in a second state to disable operation of the synchronous data transmission and reception circuits within the memory device.