Soft Circuitry research in the FAN Club

Overview

This research is founded upon the use of configurable logic technology, currently provided in the form of Field-Programmable Gate Array (FPGA) chips. The over-arching question is how traditional computer design will change with the advent of soft circuitry - we advocate a move from a one-dimensional co-design point of view to a three-dimensional co-design point of view. Although configurable logic is the catalyst for this, the ideas also have relevance to the process of designing and programming/configuring system-level integrated (SLI) chips too.

A recent publication on the overall philosophy is:

This research has application in our flexible architecture for networking applications research.


Underpinning technology

The work has been strongly based upon an FPGA technology rooted in the Ph.D. work of Tom Kean at Edinburgh, which led to Algotronix Ltd and its CAL1024 FPGA chip. Tom has a photo-history of this. Algotronix became part of Xilinx Inc in 1993, and the CAL1024 evolved into "CAL 2", the Xilinx XC6200 series. Virtual Computer Corporation (VCC) led the way in making the XC6200 available on a plug-in PCI bus board for PCs. Xilinx discontinued development of the XC6200 in 1998. Our work has now moved to the new mainstream line from Xilinx - the Virtex family. We thank Algotronix, Xilinx and VCC for their support over the years, in the form of pre-release and no-cost hardware and software, and other goodies.

Some of our tools for using the XC6200 board under Linux are available for general use. Others are available on request.


Areas of investigation

Introduction

As an introduction, here are two sets of slides from the Dagstuhl-Seminar on Dynamically Reconfigurable Architectures, held in February 1998: A second Dagstuhl-Seminar on this topic was held in June 2000 - Gordon Brebner was one of the organisers.

The four sections below concerns the four main strands of work carried out in the past, and all continuing now and in the future. There is much still to be done.

Novel programming tools

One area investigated extensively has been systems for allowing programs and programmers direct access to configurable logic circuitry, enabling intimate interaction not possible when conventional hardware design tools are used. Some publications: We are now collaborating with Steve Guccione at Xilinx, aiming at convergence with his JBits (formerly JERC) tools.

Virtual circuitry

A second area has been systems for supporting "virtual circuitry" - a circuit analogue of virtual memory. Here are some recent publications:

Circlets

The third area has been systems for supporting "circlets" - logic circuit equivalent of program applets. Here is a recent publication:

Novel architectures

The fourth area has been novel FPGA architectures for supporting soft circuitry. We have designed a self-timed FPGA technology, and simulated but not physically implemented it. Asynchronous technologies offer benefits for both using and managing soft circuitry, since one is liberated from worrying about global clock signals. For much more information, see a collection that includes a thesis and several papers.

Future work will concern not only architectures of isolated configurable logic arrays, but also the incorporation of such arrays into system architectures, with novel interfaces to processor cores and memories. System-level integrated chip design is central to this project, as is the use of optoelectronics as an integrated system component.


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Gordon Brebner, questions to <gordon@dcs.ed.ac.uk>, 26 March 1999