viewpoints Vdoi:10.1145/1941487.1941501 Jason Fitzpatrick Interview an Interview with steve furber Steve Furber, designer of the seminal BBC Microcomputer System and the widely used ARM microprocessor, reflects on his career. tePhen ByraM FurBer is the a founder. I went along to the very first ICL Professor of Com- meetings and started building com- puter Engineering in the the BBC micro was puters for fun, which was fairly scary School of Computer Sci- just the front end in those days because the components ence at the University of of something that had to be ordered from California by SManchester, U.K. Furber is renowned mail order using a credit card. I was a for his work at Acorn Computers Ltd., was designed as student so credit cards were fairly scary where he was a principal designer of then; using them internationally was the BBC Microcomputer System and a dual processor even scarier. But we got the micropro- the ARM microprocessor, both of from the outset. cessors. My first machine was based which have achieved unique historical on the Signetics 2650, which not many significance. people have heard of these days. It The BBC Micro platform was funda- had a full kilobyte of static RAM main mental to computing in British educa- memory. I assembled the circuit board tion in the 1980s and directly led to the using Verowire, which is a little wiring development of the ARM architecture. of the information age (see http://www. pen where you hand-wired the things The ARM architecture is the most wide- computinghistory.org.uk/.) A video of together; you soldered it, which melted ly used 32-bit RISC architecture and the the interview is available at http://www. the insulation and made the connec- ARM processor’s power efficiency—per- computinghistory.org.uk/det/5438/ tions. I understand it gave off carcino- forming the same amount of work as Steve-Furber-Interview-17-08-2009/; a genic vapor, but it hasn’t got me yet. other 32-bit processors while consum- condensed version of the interview is That’s how I built these things. I ing one-tenth the amount of electric- presented here. built myself a small rack—I couldn’t ity—has resulted in the widespread afford a commercial rack, so I made dominant use of the ARM processor in I’d like to talk to you about your in- one and got the 2650 system going. mobile devices and embedded systems. volvement with acorn, and what it’s In the Processor Group, enthusiasts Furber is a Fellow of the Royal Acad- led to today. exchanged notes with each other. I re- emy of Engineering, of the Royal So- I was at the University [in Cam- member Sophie Wilson coming to my ciety, the IEEE, the British Computer bridge]; I read maths as an under- house for one meeting of the Proces- Society and the Institution of Engi- graduate and I went on to do a Ph.D. sor Group, looking at my machine and neering and Technology (IET), and was in aerodynamics. During my Ph.D. I poking away at it—finding faults in appointed Commander of the Order of got interested in aspects of flight, and the memory and stuff like that. Then the British Empire (CBE) in 2008. then I heard about the formation of while I was still a Ph.D. student in the Jason Fitzpatrick, a computer his- the Cambridge University Processor Engineering Department, Hermann torian and the curator at the Centre Group. I thought maybe I should join Hauser came knocking on my door and for Computing History at Suffolk, up with these guys and see if I could explained that he and Chris Curry were U.K., conducted an extensive interview build myself a flight simulator or some- thinking of starting a consultancy com- with Furber on behalf of the museum, thing like that. I was involved in the pany in the microprocessor business. which is dedicated to creating a perma- University Processor Group from its They had been looking to the Univer- nent public exhibition telling the story foundation although I wasn’t actually sity Processor Group as the source of 34 CommunicatIons of the aCm | may 2011 | vOl. 54 | nO. 5 viewpoints technical people who might be able to you interfered with it, it should defi- think the Altair had probably appeared help them; he asked me if I was inter- nitely not pay out. The things were about this time in the States. ested. I said, “Well, I’m just a hobbyist. tested by plugging a mains adapter In the University Processor Group, I’ve been doing this for fun. But if you into the wall, plugging the fruit ma- the real men built computers with TTL. think I can help, I’m willing to give it a chine into one socket, and an arc weld- It was only the wimps like me that used go.” That’s how I joined the embryonic ing transformer into the other. Some- newfangled microprocessors, which Acorn, before it was Acorn. body welded metal together while you were kind of cheating because you got operated the fruit machine to see if the too much functionality in one package. V Was it based inside sinclair’s building thing was robust to sparking. But yes, microprocessors were just en- at the time? tering the public consciousness, so the Yes, the first things we did were in fantastic! the feeling at that time was MK14 from Science of Cambridge was the Science of Cambridge Building in very much of the hobbyist. you just en- an example of a microprocessor on a King’s Parade. Chris Curry was set up joyed doing that kind of thing, and the printed circuit board with a hexadeci- running Science of Cambridge with whole industry has pretty much come mal keypad and seven segment display; Clive. Hermann and Chris did bits of out of that. Is that fair to say? you could put assembly code into it and Acorn work in there. In fact the first Yes, that’s right. We are talking about make it run. Sophie saw the MK14 and thing I did for Acorn was actually not for the late 1970s before the IBM PC started, said something which she said many Acorn, it was for Science of Cambridge. before the Apple II had appeared. There times—basically, “I could do better I hand-built the prototype MK14; I got were some very basic box machines. I than that.”— and she went home over a circuit diagram and built one using Verowire, soldering in my front room. The MK14 was basically a copy of the National Semiconductor SC/MP devel- opment kit. They had taken what was a masked program ROM from the de- velopment kit and copied it into two fusible link PROMS for the MK14, and they managed to copy it wrong. So I de- bugged this thing in my front room. That was the first piece of work I did for them. Then Chris and Hermann got a con- tract to do some development work on microprocessor controlled fruit machines, which were very new at that time. Up to that date fruit machines had all been controlled by relays and so on; this was an early attempt to do micro- processor stuff. We used two SC/MPs in a rack to control the fruit machine. In fact, the software for that was boot- strapped from the 2650 machine I built in the Processor Group; it was used as a dumb terminal into the SC/MP devel- opment kit, and we brought this fruit machine controller up. The main chal- lenge in those days was to make these things robust. Very early on people had discovered if you just sparked electron- ic cigarette lighters next to the fruit ma- chine, they would often pay out. yes, the program counter jumps off er B ur somewhere and anything can happen! F e V e Yes. So that was when Sophie Wil- st F son came in. She designed an FM re- y o S e ceiver front end that would trigger T our whenever you flicked one of these ciga- C ph rette lighters and cause the SC/MPS to ra G o reset; it would definitely not pay out. T o H P [laughs] That was the requirement—if may 2011 | vOl. 54 | nO. 5 | CommunicatIons of the aCm 35 viewpoints Easter holiday and came back with a neither Z80 nor CP/M, although a couldn’t let them in. Nobody was ex- design she called the Hawk, which was little bit later you could buy a Z80 sec- pecting this, either. 6502-based. Hermann looked at this ond processor to run CP/M; we kind of The machine was first sold in Jan- and thought he could sell it; that be- met the spec in the end. But no, they uary of 1982, so this may have been came the Acorn System 1. The name were sufficiently convinced by what later in 1982. Acorn was introduced originally just we could do with the 6502 that they as a trading name. The company was moved the spec to the machine that and that was the first time you thought called Cambridge Processor Unit Ltd. Acorn had already begun to get on the this is big? drawing board. The Proton was always Well, this is when you first felt the If you look at those machines today, designed as a dual processor. The fact scale of public interest.