The Third Way Neither Hardware Nor Software Gordon

The Third Way: Neither Hardware Nor Software Gordon Brebner Division of Informatics University of Edinburgh 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh

Hardware and software • Hardware connotations: – logic circuitry, datapaths, processors, etc. – computer architecture – fixed (hard) • Software connotations: – programs, scripts, GUIs, etc. – computer algorithms – flexible (soft) 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 2

Dynamically reconfigurable architectures • Alternative phrase (one of several): – run time reconfigurable systems • Not just under the ‘hardware’ heading: – because not fixed, by definition • Not just under the ‘software’ heading: – because not programs etc. , by definition • So, a ‘third way’ is needed 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 3

The bigger picture • Traditional view of computing systems: – von Neumann style processing elements – maybe short-distance parallel interconnection – maybe longer-distance network connectivity • Some new technological influences: – system-level integrated chips – configurable logic arrays – photonic technologies 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 4

The bigger picture • Future view of computing systems: – networks of diverse programmable information handling components, from chip level upwards – information is digital, analogue, approximate, … – components are electronic, photonic, micromechanical, … – communication is the key concept • Stand-alone computers, as such, will fade away 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 5

The third way • Backdrop is provided by the ‘big picture’ • Expressing diverse programmability: – ‘architecture’ to mean the programmable thing? – ‘algorithm’ to mean the programming? • Expressing logical and physical connectivity – much inspiration from (inter-)networking • What are apt levels of abstraction? 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 6

Programmability • Human-programmed includes: – program-style ( Turing machine, RAM models of computation) - control flow – circuit-style ( boolean circuit, algebraic circuit models of computation) - data flow • Self-programming - adaptive systems • Applies equally to computation and communication, as these concepts merge 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 7

Connectivity • Absolute and relative positions of communicating components: – determined by external-world location/mobility – selected by human programmer – selected by automated process • Similar for communication channels • Expression of parallelism and interaction 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 8

Towards the third way • The bigger picture context is in its infancy • Resist existing abstractions that are general enough, but perhaps abstract away too much • First investigate some incremental stepping stones towards future systems design, rather than trying to solve everything too soon • Be prepared to invent new information handling models, and system design processes 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 9

Personal investigations • Focus is on reconfigurable logic as an information handling component, for example: – interaction with processors and memories, particularly in systems on chip – circuit modification and self-modification during execution – portable and partitionable abstractions of circuitry – asynchronous circuitry 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 10

Summary • Hardware - just the physical tangible technology (no structure implied) • Software - just the programming information (no type of programmable system implied) • The third way: – how hardware and/or programmable subsystems are harnessed to provide a fixed system or a software programmable system 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 11

Conclusion • These are exciting times for information architectures, and there is a lot of interesting research to be done - good news for us • Must break down barriers between and within areas - computing, electronics, photonics, . . . • There are very many potential benefits, from the ‘disappearing computer’ in the appliance or location, to grand challenges and e-science 25 -30 June 2000 Dagstuhl-Seminar 00261 Gordon Brebner, University of Edinburgh 12