808 lines of BBC BASIC and a dream: Arm architecture turns 40
- Reference: 1745922068
- News link: https://www.theregister.co.uk/2025/04/29/arm_40/
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A BBC Micro signed by Arm co-designer Sophie Wilson and her co-boffins at the Centre For Computing History, Cambridge – click to enlarge ( Pic: Richard Speed )
It is difficult to overstate the significance of the Arm architecture and its impact on the modern world. However, the prospect of powering billions of gizmos was not top of mind for Acorn staffers gathered around a BBC Micro.
The computer, a familiar sight in classrooms throughout the UK and plugged into the televisions of well-heeled parents, allowed the attachment of a second processor. There was a unit with an additional 6502 processor, another contained a Z80 processor. And this one could accept Acorn's new RISC chip, freshly stamped out by VLSI.
At 3pm on April 26, 1985, having been plugged into the test board attached to the BBC Micro, power was introduced and the processor worked. Sophie Wilson, author of BBC BASIC and one of the brains behind the Arm chip, copied an Arm version of the BASIC interpreter and tried a command. Everything checked out.
"It did not say, 'Hello world, I am Arm,'" laughed Wilson at the [2]CCH event . "I think that's one of Hermann's [Hermann Hauser, who set up Acorn Computer with Chris Curry] apocryphal stories! But it did say Pi."
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By then, Wilson was already confident that the chip would work. Loading was complete, and the Tube, an expansion interface for the BBC Micro, was up and running. "Everything must be working," she recalled. And it was. Almost.
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One small bug slipped through the net, a classic combination of instructions that could result in some erroneous output. However, corks were popped long before it was uncovered.
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Arm @ 40 event speaker line-up (pic: Centre for Computing History) – click to enlarge
A ten-person team had spent 18 months working on the low-power RISC chip, and it had pretty much worked the first time. Famously, a problem with the board meant that a connected ammeter registered zero power consumption – the design was supposed to sip power compared to other chips, but not to this extent. According to the CCH, the actual figure was around 120 mW, considerably below the 2,000 mW demanded by some contemporary CISC processors.
Also speaking at the CCH event was Steve Furber, famous for his work at Acorn and more recently the [7]SpiNNaker architecture. "I was responsible for the micro-architecture [of the first Arm processor]," he said, "which was captured in a reference model written in BBC BASIC.
[8]Qualcomm says license fight was because Arm wants to make its own server chips
[9]Avnet accuses Arm chip slinger Ampere of screwing it over on server deal
[10]RISC OS Open plots great escape from 32-bit purgatory
[11]Arm reckons it'll own 50% of the datacenter by year's end
"The fact that you can write the whole Arm description in 808 lines tells you how simple it was."
And today's Arm CPUs? Some good-natured heckling from the audience put the figure as the output of 200 engineers over two years. Quite a bit more than the 808 lines Furber recalled for the effort more than 40 years ago. Another wag in the audience suggested that without comments, the line count might be even less, to which Furber laughed and said: "Well, it was written in BBC BASIC, which is a self-commenting language."
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Arm exhibit at the Centre for Computing History (pic: Centre for Computing History) – click to enlarge
Furber and Wilson were joined by other luminaries from the early days of the processor, including Hugo Tyson, Lee Smith, Arthur Norman, and Jamie Urquhart, in a refreshingly modest retelling of the Acorn and Arm story.
"We thought it was a really obvious way to build a processor and everybody would be doing it," said Wilson. "That turned out not to be the case."
That processor, which was first fired up 40 years ago, was a glimpse into the future. It would take bigger companies many years to start seeing things the same way as that early team.
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The Arm exhibit is now a permanent fixture at [14]Cambridge's Centre for Computing History , and is well worth a visit. The museum also has a range of computers, along with a smattering of vintage gaming consoles, with which visitors can play or, in the case of this writer, be bad at. ®
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[1] https://regmedia.co.uk/2025/04/28/bbc_micro.jpg
[2] https://www.computinghistory.org.uk/det/74205/The-40th-Anniversary-of-the-ARM-1-Chip-Saturday-26th-April-2025/
[3] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/systems&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aBFL7Wpvd-6awguK-FaGrgAAAko&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[4] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/systems&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aBFL7Wpvd-6awguK-FaGrgAAAko&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[5] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/systems&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aBFL7Wpvd-6awguK-FaGrgAAAko&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[6] https://regmedia.co.uk/2025/04/28/arm_at_40.jpg
[7] https://www.theregister.com/2017/10/19/steve_furber_arm_brain_interview/
[8] https://www.theregister.com/2025/04/24/qualcomm_arm_licensing_lawsuit_amendment/
[9] https://www.theregister.com/2025/04/14/avnet_sues_ampere/
[10] https://www.theregister.com/2025/04/01/risc_os_open_moonshots/
[11] https://www.theregister.com/2025/04/01/arm_datacenter_cpu_market/
[12] https://regmedia.co.uk/2025/04/28/arm_display.jpg
[13] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_onprem/systems&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aBFL7Wpvd-6awguK-FaGrgAAAko&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[14] https://www.computinghistory.org.uk/
[15] https://whitepapers.theregister.com/
Re: I would like an ARM 1
I got me a mint restored Master 128.
Gonna strap a PiTube and the SCSI to SD card to it and design me some cartridges.
Nobody ever did anything exciting with the carts.
I will fix this.
Re: I would like an ARM 1
Still gutted I had to pass on a new sealed box (One of about 6) BBC Master 128 back in 2007/8 (Pulled up from the bowels of Somerset County Councils basement).
Beer
That is all.
On a related topic in the Science Museum they have a room of old tech and it was gratifying or depressing to see how many of the items I still own. I do have an Archimedes original bought second hand of course but not too long after it was new.
Science Museum
I shed a tear in there last week as so much in the large "communications" room was the history of my life's work.
Re: Science Museum
Maybe it's my age - and possibly yours - but the progress from chip wrapping to history seems to have speeded up even more than CPU clocks.
>depressing to see how many of the items I still own.
Even more depressing when you see items you still use, and rely on, at work
Such an obvious design, and one that today powers the majority of actual devices in the world.
I remember learning about RISC in 1985 at uni, and thinking "this is clever" but having absolutely no idea of course of what was to come.
"RISC architecture is going to change everything" - Acid Burn, 1995
"RISC architecture is going to change everything"
Considering ARM is likely the dominant architecture in smart phones, TVs etc etc, I guess it did.
All considered I should think more of a curse than a blessing.
I mean, he wasn't wrong.
*she.
Crash Override was the he.
1985
I didn't realise ARM went back that far - it's coeval with the first commercial MIPS processor and well before the Sparc et al.
The Inmos Transputer also surfaced around that time. UK innovation was apparently alive and well in the 1980s under Maggie Thatcher... hang on that can't be right. :)
History not infrequently bites preconceptions on the bum.
Re: 1985
It was, until the neoliberal policies finally killed them
Re: 1985
I remember the big selling point of the Neve/AMS Audiofile editing system in the mid 1980s was the fact it was powered by an Inmos Transputer. I went from 78 or 33 rpm gram decks, sticky splicing tape, ¼" magnetic recording and optical film tracks to 8 tracks of PCM audio at 48kHz in a few weeks. Transformed to world of TV and audio post production.
Re: alive and well in the 1980s under Maggie Thatcher
No, she killed Inmos. Thomson bought the IP.
Thatcher only wanted trading, not manufacturing. Sadly many economics books are marketing handbooks: "don't own the mill, outsource".
The Transputer was brilliant compared to 386. So was ARM.
1984: Release of 16 bit transputer
1985: Release of 32 bit T414.
The 80386 pre-production samples was October 1985. The 80286 was a flawed design compared to 68000 and ARM 16 bit CPUs.
Re: alive and well in the 1980s under Maggie Thatcher
> sadly many economics books are marketing handbooks: "don't own the mill, outsource".
I have read a good many and cannot recall one that did. Its not even the role of an econ textbok to give business advice. Maybe you can point to an example?
Re: 1985
Yup, it's been around almost as long as those of us currently filling the roles of wise old greybeards at our respective employers, which doesn't make me suddenly feel old at all...
One of my best mates at school got an Archimedes A310 more or less as soon as they became available, and a few years later I also had access to an A3000 via the school where my mum worked, and it was obvious from playing around with them just how special a machine it was. Little did I realise at the time how much of that was down to the ARM at its core, or how utterly indispensable that processor architecture would then become to the modern world. Having then gone on to earn a comfortable living as an embedded systems developer, much of which has been spent working on one or another flavour of ARM-based microcontrollers, I now find myself thinking back to those childhood times with a sense of nostalgia even warmer and fuzzier than usual.
So a very well deserved hats off to all involved in its development - despite being a Spectrum and Amiga fan back then, I always had a soft spot for Acorn's offerings and consider myself exceedingly fortunate to have been in a position to get so much hands on experience with them at the time.
Re: 1985
The RISC-OS was a bit clever aswell.
File ID types, so you can have .bak files for different apps without stepping on each other.
Being able to shrink the font cache or screen resolution in the GUI if your program needed a bit more space.
And it could emulate a DOS PC in software, faster than a real IBM XT
A game of Zarch anyone?
For commemorative purposes.
Re: A game of Zarch anyone?
Afraid I've only got !Lander
Am I sad in keeping an eye on Ebay for an ICL DRS in that old cream and brown colour, that I used in college, good memories, actually met my future wife on the same computer course.
Sophie
I don't know if you drink beer, but I would happily buy you one. What genius!
Re: Sophie
She's completely teetotal and always has been. This is probably why she can remember stuff.... I'll take it on her behalf! :-)
No need really, CCH bought us lunch, more than happy with that. Cheers!
Re: Sophie
Wow! You folks really exist! (always amazes me here at ElReg Saloon) ... 3ʳᵈ usual suspect from the right in that CCH multi-mugshot "police" line-up hey ... I see ... yup, that's the one officer, definitely did it! ... ;)
Cheers!
Re: Sophie
It looks more like the poster for a "Calendar Girls" remake of The Full Monty
Anybody know if that 808 line program is available?
See subject. ;)
Re: Anybody know if that 808 line program is available?
or is it 404?
There is a fantastic multi-part series of articles on Ars Technica covering the creation of ARM, how it came to be built, why its power consumption was so low, and of course what happened over the following years with ARM being spun off from Acorn. It's well worth a read.
And Happy Birthday ARM!
"It would take bigger companies many years to start seeing things the same way as that early team."
Maybe not bigger companies but MIPS was launched about the same time and SPARC a year or so later.
Interesting
This is similar to a chip design system developed at the WRL of DEC. Where they linked all the elements together as segments of code in C.
Sounded like a clever plan.
I would like an ARM 1
I saw one on e-bay go for more money that I could afford, years ago back in the days before people were paying silly money for retro equipment. I have a battered 6502 cheese wedge, and I can play Elite Executive Edition on that, but I'm happy :-) I have three Beebs and they keep me busy. Along with my six ZX81's of course. ;-)