[HN Gopher] A technical history of Acorn Computers
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A technical history of Acorn Computers
Author : xyzzy3000
Score : 123 points
Date : 2025-03-10 14:35 UTC (1 days ago)
(HTM) web link (www.mcmordie.co.uk)
(TXT) w3m dump (www.mcmordie.co.uk)
| amiga386 wrote:
| Ah, the delights of a page that covers 26 years of history and
| hasn't been updated for 21 years
|
| I can at least say that in the meantime, RISC OS is still alive
| and now open, available from https://www.riscosopen.org/, and
| most people will know the ARM company and its architectures went
| from strength to strength, even if the RISC PC faded away.
| dcminter wrote:
| Some time when I have some spare time I must fish out a Pi and
| try it out - I was deeply envious of the Archimedes owner I
| knew back in the day!
| xyzzy3000 wrote:
| I'm not sure what the state of Pi 5 support is, but RISC OS
| seems to work on the Pi 1, 2, 3 and 4.
|
| ArcEm is a decent emulator for the Archimedes series, and
| RPCem is the equivalent for the RiscPC which succeeded it. OS
| ROM images are available from a variety of places.
|
| For floppy disk emulation, ADFFS is what you are looking for,
| and some games have been released in this format with the
| consent of the copyright holders.
| jlarcombe wrote:
| Don't think Pi 5 can run 'supervisor code' (in old ARM
| language) in 32-bit mode, so RISC OS surely won't run. The
| bulk of it is written in assembler so reworking it to
| AArch64 would be an epic task. Probably take no longer to
| rewrite those bits in a higher-level language, for much of
| it.
| skissane wrote:
| DEC had a similar problem when porting VMS from VAX to
| Alpha - significant chunks of it were written in VAX
| assembly.
|
| They came up with a rather ingenious solution - a
| compiler from VAX assembly to Alpha. And that was carried
| forward into the Itanium and now x86-64 ports, so even
| latest OpenVMS for x86-64 still contains some VAX
| assembly code, but it is compiled into LLVM IR and then
| the LLVM backend converts it to x86-64 ELF binaries.
|
| No reason in principle why someone could not do the same
| thing with the 32-bit ARM assembly code in RISC OS.
| Likely would be easier than rewriting it all in a high-
| level language
| chasil wrote:
| IIRC there was "macro32" which could compile VAX machine
| code to Alpha, and also VEST, which was a virtual
| machine.
|
| I've used neither.
| skissane wrote:
| Yes "MACRO-32" [0] is what I'm talking about and is still
| around - from Alpha it was ported to Itanium and now
| x86-64. Although to clarify, my understanding is it
| doesn't take machine code as input, rather macro
| assembler source code - although I suppose you could use
| a disassembler to turn your VAX binary into assembler
| source and then try compiling it with MACRO-32.
|
| VEST wasn't actually a VM per se, it was a static binary
| translator - read in an OpenVMS VAX executable, write out
| an OpenVMS Alpha executable. VEST was only ever available
| for Alpha, but HP then created AEST which could do the
| same thing to translate Alpha executables to Itanium-and
| you could use VEST then AEST in sequence to port a VAX
| executable to Itanium.
|
| However, VSI have said they have no plans to create an
| "IEST" to port Itanium executables to x86-64. I believe
| they face two big difficulties: (a) Itanium is a very
| complex and non-traditional architecture which makes
| binary translating it more of a challenge than it would
| be for a more mainstream architecture (b) legal risk due
| to aspects of it being covered by Intel patents (and
| unclear if Intel would license those patents on terms
| which would make an "IEST" commercially viable)
|
| [0] https://en.m.wikipedia.org/wiki/VAX_MACRO
| sillywalk wrote:
| Tandem used something similar called The Accelerator to
| translate binaries from their proprietary CISC chips to
| MIPS, including parts of the NonStop operating system.
|
| See Tandem Systems Review, Volume 8 Number 1 - Spring
| 1992
| eftpotrm wrote:
| HP did the same when migrating away from the PA RISC
| architecture.
|
| IIRC as part of their testing they set it up so it would
| ingest, recompile and output code for the same
| architecture, and found that it could produce speed
| improvements due to context awareness.
| sillywalk wrote:
| > recompile and output code for the same architecture,
| and found that it could produce speed improvements due to
| context awareness.
|
| That sounds like HP's Dynamo.
|
| https://dl.acm.org/doi/pdf/10.1145/358438.349303
| eftpotrm wrote:
| That's it! Thanks :-)
| lproven wrote:
| > Don't think Pi 5 can run 'supervisor code' (in old ARM
| language) in 32-bit mode, so RISC OS surely won't run.
|
| The RISC OS folks are well aware of the issue.
|
| There are discussions about what to do underway.
|
| One idea that I sort of like is a tiny sort of hypervisor
| in Arm64 code, that runs an Arm32 "VM". Then RISC OS
| executes in the VM.
|
| It's not fully native, no, but with the speeds involved,
| it would be usable.
|
| There is a lot of prior art for this approach:
|
| 1. RISC OS already faced a 24-bit to 32-bit migration,
| and one bit of the legacy of that is an emulator for
| running 24-bit RISC OS apps on 32-bit RISC OS, called
| Aemulor.
|
| https://en.wikipedia.org/wiki/Aemulor
|
| 2. There is of course a whole industry running x86 PC
| emulators on x86 PCs. The one that started it is called
| VMware and it did quite well.
|
| But others copied it: e.g. Connectix ported VirtualPC
| from Classic PowerPC MacOS to Windows. I interviewed the
| company's founder and chief scientist Jonathan Garber.
|
| https://en.wikipedia.org/wiki/Webcam#Early_development_(e
| arl...
|
| At that time, x86 didn't do hardware virtualisation. So,
| VMware just used a software emulation for ring 0 code.
| Garber told me that once he saw how VMware did it, he
| realised Connectix could do that, too. He then told that
| it was much easier than running x86 code on PowerPC. With
| a grin he said that it was not only easier, the
| performance was excellent: the instruction sets were a
| _really_ close match. ;-) So the emulator was very nearly
| achieving 1:1 code density: one instruction for one
| emulated operation.
|
| 3. When Apple moved Classic MacOS from 680x0 to PowerPC,
| it did it using a tiny "nanokernel" containing a 68K-to-
| POWER ISA emulator.
|
| https://en.wikipedia.org/wiki/Mac_OS_nanokernel
| jlarcombe wrote:
| yes, surely a good approach, and as you say the
| performance is likely to be fine given the vast increase
| in raw speed since the old days...
| sammyteee wrote:
| A good read!
|
| I like that all the sites linked in the banner, no longer exist!
| https://www.mcmordie.co.uk/public/apeople.shtml
| xyzzy3000 wrote:
| I particularly liked the tiling background, which may well have
| been created using Texture Garden https://texturegarden.com/ by
| Tim Tyler (of Repton fame, for the BBC Micro fans)
| II2II wrote:
| There are plenty of links on other pages that lead to
| functional websites of various vintages (the keyword being
| vintage). Just go to https://www.mcmordie.co.uk/ and start
| exploring.
| dcminter wrote:
| Someone will be along in a minute to tell you to watch Micro Men,
| an amusing and fairly accurate BBC dramatization of the
| Sinclair/Acorn rivalry :) but I'm here to recommend that you
| watch the Computer History Museum's interview with Hermann Hauser
| the erstwhile director of Acorn - he's very charming:
| https://m.youtube.com/watch?v=Y0sC3lT313Q
|
| I'm fairly sure they've got one with Chris Curry too, but I can't
| spot it just now.
| amiga386 wrote:
| It would appear you can watch Chris Curry and Hermann Hauser
| watch _Micro Men_ : https://www.youtube.com/watch?v=yaonVYOTSsk
| -- and then have a post-viewing chat:
| https://www.youtube.com/watch?v=l4I2ktcWdJM
|
| "I saw the first five minutes and had to run away, because I
| couldn't bear to see myself portrayed by Martin Freeman" --
| Chris Curry
| timthorn wrote:
| Which was hosted by the Centre for Computing History!
| xyzzy3000 wrote:
| It's an entertaining watch, although a fair bit of dramatic
| licence is taken when depicting various anecdotes that would be
| well-known to readers of The Micro User and similar magazines
| of the time.
| dboreham wrote:
| I had high hopes that the depiction of Uncle Clive's groupie
| encounter was entirely accurate.
| xyzzy3000 wrote:
| Apparently the pub altercation wasn't far off.
| westi wrote:
| Some great memories here.
|
| Somewhere in my parents attic is my RISC PC 600 and 486 Co-
| Processor card. Not sure if they also have the A3000 we had
| before that.
| xyzzy3000 wrote:
| If possible, get the batteries removed from the motherboards -
| the leaks cause immense damage.
|
| Rechargeable AA batteries in a battery holder are a sensible
| replacement.
|
| If the hard drive has packed in then a SD to IDE/PATA adapter
| is available.
| simonjgreen wrote:
| My secondary school was full of these in the computer labs.
| Great bits of kit :) The dual boot between architectures blew
| my mind at the time, and frankly is still pretty extraordinary.
| And unlike most boxes of the time, they even looked good!
| callumprentice wrote:
| I purchased an Acorn Atom in 1980 (the prebuilt one - a friend
| opted for the self-assembly and regretted it) and I still
| remember the thrill of setting it up and turning it on for the
| first time. It feels like I didn't sleep for a week but I suppose
| I must have.
|
| When you entered a line of their BASIC, it would check the line
| for errors. At one point, I kept getting error XX (I don't recall
| the actual number) and couldn't see the error in my code.
| Eventually figured out it meant I was out of RAM. There was only
| 2K and I think the 6502 took some and the screen too so there was
| only about 500 bytes left over. What a joy it was after I saved
| up for the 6K upgrade.
|
| And then there was the local computer club presentation that
| ruined any chance of a public speaking career.... :)
| andrehacker wrote:
| O man, good times. I remember soldering RAM chips "piggyback"
| style, then upgrading to 64K of RAM, and adding 8 special-
| purpose ROMs (from utilities to a spreadsheet program). I even
| installed a color video board-- all of this inside the Acorn
| Atom itself (which was a keyboard-style computer, similar to
| the C64).
|
| The Atom also brought together a community of hardware and
| software enthusiasts through Atom Computer Clubs. These clubs
| were doing amazing things, including the development of Z80 co-
| processors and even running CP/M. While Acorn moved on from the
| Atom to the BBC Microcomputer, the clubs kept the Atom alive
| well beyond its prime.
|
| It's fascinating to look back and realize that the same team
| behind the Atom went on to create the ARM processor, which,
| interestingly, shares a striking similarity in its instruction
| set with the 6502.
| callumprentice wrote:
| Good grief - 64K - what on earth did you do with all that
| storage :)
| chasil wrote:
| Do you have more details on the striking silarity?
|
| All the wiki mentions is optimized memory usage.
| lproven wrote:
| Quora has some informative responses:
|
| https://www.quora.com/Is-ARM-RISC-derived-or-inspired-by-
| the...
| ajb wrote:
| That first reply (in the quora link) is a bit too
| dismissive
|
| A lot of the instruction _names_ are the same, but the
| apparent similarity becomes less once your start using
| them. Using the same names was probably very convenient
| given that Acorn 's previous computers used the 6502, and
| it would have helped the programmers who need to
| transition.
|
| But the machine was quite different to program, and the
| Arm made more innovations than just being a 6502 with
| more registers. Every instruction being potentially
| conditional, and every instruction being able to make use
| of the barrel shifter, were both quite radical at the
| time and contributed a lot to the density of code in
| those machines (although they are inconvenient to out-of-
| order microarchitectures, so have been dropped from V8)
| andrehacker wrote:
| Sophie Wilson (the designer of the original ARM instruction
| set) said this when asked which CPU architecture she
| admired:
|
| Sophie Wilson, chief architect of ARM and more recently of
| the Broadcom FirePath October, 2001
|
| Primarily the 6502. I learned about pipelines from it (by
| comparison with the 6800) and its designers were clear
| believers in the KISS principle. Plus the syntax of its
| assembler and general accessibility of it from the machine
| code perspective. I can still write in hex for it - things
| like A9 (LDA #) are tattoed on the inside of my skull. The
| assembly language syntax (but obviously not the mnemonics
| or the way you write code) and general feel of things are
| inspirations for ARM's assembly language and also for
| FirePath's. I'd hesitate to say that the actual design of
| the 6502 inspired anything in particular - both ARM and
| FirePath come from that mysterious ideas pool which we
| can't really define (its hard to believe that ARM was
| designed just from using the 6502, 16032 and reading the
| original Berkeley RISC I paper - ARM seems to have not much
| in common with any of them!). And clearly the 6502's
| follow-up, the 65816, wasn't "clean" any more, so whichever
| of Mensch and Moore contributed what to the 6502, Mensch by
| himself was a bit at sea.
|
| Biggest object lesson was, however, National
| Semiconductor's 32016 (aka 16032): this showed how to
| completely make a mess of things. The 32016 first exposed
| the value of memory bandwidth to Steve Furber and I, showed
| how making things over-complex led to exceedingly long
| implementation times with loads of bugs in the
| implementation, and showed that however hard you tried to
| approach what compiler writers claimed they wanted, you
| couldn't satisfy them (no, I never did use a VAX). And an
| 8MHz 32016 was completely trounced in performance terms by
| a 4MHz 6502...
|
| https://people.computing.clemson.edu/~mark/admired_designs.
| h...
|
| details of the thinking process of evolving from 6502 to
| ARM in this interview.
|
| https://youtu.be/QqxThgLTLyk
|
| And, yes, striking similarity is not the best way to say
| it.
| roywashere wrote:
| I bought an Atom second-hand, it was my first 'own' computer.
| My father first had a TRS-80 model III and then an IBM clone
| XT. So the Atom was definitely less capable, but it was my own.
| I read all the accompanying manuals front to back and I read
| the computer magazines that came with it and this is how I
| learned English. I was 9 years old at that point. It came with
| schematics and of course I opened the case. I could not get the
| thing to load or save data on my dad's tape recorder. And it
| was only so much fun trying to type in a program from a listing
| which I could not save, especially taking into account my
| limited typing skills at the time and the fact that I had to do
| this while the Atom was attached to the TV in the living room.
| Still, it was a worth wile and forming experience and surely
| worth my pocket money.
|
| Later on in life, end of 90s, I was re-wiring the building of
| my students union, with a friend. Many amps main board, 380
| volts, 40 circuits or so, kind of big install. We had to create
| plans and supply them to get approval from the city or the
| utility company or the architect or such. For this we used the
| Archimedes of some guy that helped us. At this point the
| Archimedes definitely was dead as a platform, Windows 98 was
| just out. But it was still possible to use it to create
| drawings and schematics and quite capable.
| callumprentice wrote:
| Nice. I felt the same way - read that book from cover to
| cover many times.
|
| I could never afford a BBC Micro when that came out and
| certainly not the Archimedes but I always admired from afar.
| jefc1111 wrote:
| For me, all this ... computer life stuff ... started with an
| Acorn Electron around 40 years ago. At first it was just fun, and
| then I played Elite and it feels like a lot of my future was
| defined in that experience.
| simonjgreen wrote:
| Ditto. Electron and Elite with a voltmace joystick that (memory
| may be hazy) had like 20 buttons on it was mind blowing to
| child me.
| aardvark179 wrote:
| That's how I started as well. Much nicer to program than the
| spectrum, and taught me about parsing in the worst way when I
| discovered my text adventure couldn't have a variable called
| torch because it was. Parsed as to rch.
| LoganDark wrote:
| > and taught me about parsing in the worst way when I
| discovered my text adventure couldn't have a variable called
| torch because it was. Parsed as to rch.
|
| "to rch" reminds me of the "x goes to 0" meme:
| https://stackoverflow.com/questions/1642028/what-is-the-
| oper...
| tolien wrote:
| Same, and now I'm still playing Elite but just with slightly
| better graphics :-D
| tonyedgecombe wrote:
| My first computer was an Acorn System One. I spent a summer
| picking fruit at an orchard to pay for it.
|
| 1k of RAM, 512 bytes of ROM, a seven segment calculator display
| and hex keyboard.
|
| I spent hours hand assembling 6502 code for it. I even created a
| stack based language for it in an attempt to teach my younger
| brother how to program.
| xyzzy3000 wrote:
| For anyone interested in the very early Acorn era, there are
| some replica boards available here, from System 1 all the way
| up to System 5:
|
| https://theoddys.com/acorn/replica_boards/replica_boards.htm...
| Lio wrote:
| So much history here for me.
|
| One landmark buried in there was the ARM 250 chip based machines.
|
| I think they were some of the first system on a chip desktop
| computers.
|
| They lacked the glamour of the Arm 3 based machines launched
| around the same time but really they were ground breaking.
| xyzzy3000 wrote:
| I think it was possibly the first to go into a desktop
| computer.
|
| ARM250 datasheet here:
| https://home.marutan.net/arcemdocs/ARM250.pdf
|
| For Acorn, this chip really helped to bring costs down for the
| A30x0/A4000 machines - the Electron of the Archimedes era. The
| RiscPC equivalent was the A7000/A7000+ with the
| ARM7500/ARM7500FE, the FE being novel for the inclusion of the
| FPU which ARMs had traditionally not included.
| Lio wrote:
| The A7000s sort of passed me by as I had a RiscPC at the time
| (which predicatably I really regret selling).
|
| I always wanted an FPU for my RiscPC, do you know how much
| difference they made day to day?
| simonjgreen wrote:
| A nice note of recognition of the contribution of the Acorn made
| BBC Micro model A and B to millions is that the Raspberry Pi
| Model A and B were named in honour of them.
| xyzzy3000 wrote:
| I suspect that the Pi 400 kit is a nod to the Archimedes 400
| series, but I haven't seen anything to confirm this.
| lproven wrote:
| Huh. Interesting but I think it's coincidence TBH.
|
| The all-in-one Archimedes were the 3xxx series: A3000, 3010,
| 3020.
|
| https://chrisacorns.computinghistory.org.uk/Computers/A3000..
| ..
|
| https://chrisacorns.computinghistory.org.uk/Computers/A3010..
| ..
|
| https://chrisacorns.computinghistory.org.uk/Computers/A3020..
| ..
|
| That would have been a far more obvious and better fit.
|
| The Pi 400 is based on the Pi 4, so 4000 would have fit, but
| the A4000 was a classic 3-box design with a SoC:
|
| https://chrisacorns.computinghistory.org.uk/Computers/A4000..
| ..
| whywhywhywhy wrote:
| Might be a nod to Amiga 500 which was far more prolific
| outside of schools in the UK and was keyboard form factor.
| draazon wrote:
| If the page author is reading this: hello Rob!
| geye1234 wrote:
| A wonderful snapshot of the 90s web. The entirely unaffected
| tone, the lack of self-consciousness, the random content, the
| humor, the joke lists, everything. We've lost a lot.
|
| The marginalia search engine is very good at finding this kind of
| site, btw.
| junto wrote:
| My first computer was an Acorn BBC B Microcomputer. This brings
| back very fond memories of playing Repton and Elite and having to
| wait for the tape cassette to load the games.
| xyzzy3000 wrote:
| Both Ian Bell (Elite) and Tim Tyler (Repton) have fascinating
| websites of their own. Elite is there for download alongside a
| treasure trove of historical information, and Tim has a
| successor to Repton, 'Rockz', which expands on a lot of the
| concepts in interesting ways.
|
| https://timtyler.org/
|
| http://www.iancgbell.clara.net/index.htm
| owlbite wrote:
| Our first family computer was an A3000. I'm still amazed at the
| boot time on it compared to the PCs we had later (even today).
| Switch it on, beep and then almost instantly you're in a
| responsive GUI. (The wonders of storing the OS in a ROM I guess).
| johnflan wrote:
| I started with an Acorn a3020, those machines were just amazing.
| I got my first PC shortly after running Windows for workgroups
| 3.11 jeez it felt like a step backwards. If Acorn started in the
| Silicon Valley, we'd probably be using them today.
| Lio wrote:
| One small error I've noticed on the Phoebe page, the man who
| killed Acorn was a guy called Stan Boland not Sam Boland.
|
| I leave someone with better knowledge to tell that one but it's a
| pretty sad story.
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(page generated 2025-03-11 23:02 UTC)