The 72V291 is a 128K x 9 SuperSync FIFO memory with clocked read and write controls. It's a functionally compatible version of the 72291 designed to run off a 3.3V supply for very low power consumption. The Frequency Select pin (FS) has been removed, thus it is no longer necessary to select which of the two clock inputs, RCLK or WCLK, is running at the higher frequency. The period required by the retransmit operation and the first word data latency period is now fixed and short. (The variable clock cycle counting delay associated with the latency period found on previous SuperSync devices has been eliminated on this SuperSync family.)