A FIFO Ring Performance Experiment

We describe a high-speed FIFO circuit intended to compare the performance of an asynchronous FIFO with that of a clocked shift register using the same data path. The FIFO uses a pulse-like protocol to advance data along the pipeline. Use of this protocol requires careful management of circuit delays within its control circuits, as well as in the coordination of control signals with movement of bundled data. In simulations using hSpice, the throughput of the asynchronous circuit matches that of a two-phase clocked design. We fabricated 50 parts through MOSIS using their 0.6 micron design rules. We estimate from test measurements that the internal FIFO stages could support a maximum throughput from 930 million data items per second for the slowest of the 50 chips to 1126 million per second for the fastest chip. All 50 samples operated correctly as 3.3 V nominal Vdd varied from 1.67 V to over 4.8 V, with corresponding changes in operating speed and power as the supply voltage changed.