The SN74V263, SN74V273, SN74V283, and SN74V293 are exceptionally deep, high-speed, CMOS first-in first-out (FIFO) memories with clocked read and write controls and a flexible bus-matching x9/x18 data flow. There is flexible x9/x18 bus matching on both read and write ports. The period required by the retransmit operation is fixed and short. The first-word data-latency period, from the time the first word is written to an empty FIFO to the time it can be read, is fixed and short.