Pipelining communications in large VLSI/ULSI systems

Abstract

A simple and very effective solution to the delay incurred while propagating data through long interconnection wires is presented. Such delays can be found in large VLSI/ULSI or wafer scale systems. The basic idea of the technique relies on the fragmentation of the wires and in reconnecting them with a special device called repeater in order to form a bidirectional pipeline. A method for determining the optimum configuration of the pipeline is presented. It is shown that, even in presence of an appreciable skew in synchronous systems, the technique improves the transmission speed by 150% for 32-byte messages, when a 10 cm 8-bit bus implemented in a 1.2 /spl mu/m CMOS technology is used. The improvement increases for longer messages and for larger skews. It is also shown that the actual transmission time is close (to within a factor of 2) to the theoretical limit that could be achieved with a zero-length wire. A method based on repeaters operating at a multiple of the basic system clock frequency is also proposed. It is shown that this technique may speedup data transfer by an order of magnitude. The extension of the technique to asynchronous self-timed repeaters is also discussed. Finally, a VLSI implementation of the synchronous reconnection device is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>