Strong ARM
Powering the A305 and the other Archimedes was the 32-bit ARM Risc (Reduced Instruction Set Computing) chip, developed by Acorn as the replacement for the 6502 processor it had implemented in its Atom, BBC and Electron micros during the early 1980s.
Such was the power of the ARM, wrote Pountain, that the Archimedes' software sprites could bounce around the screen as smoothly as the hardware-managed sprites offered by the likes of the Amiga and Commodore 64.
From the Archimedes demo disk: David Braben's Lander... later known as Zarch
The Acorns shipped with a demo game written by David Elite Braben simply called Game 1 – it was also labelled Lander and was the foundation for Braben's Zarch game. You flew polygon-built ship over a 3D landscape, complete with real physics and particle effects. "Astonishing," Pountain called it.
"Nothing," he wrote, "could better illustrate the way a quantitative jump in processing power can lead to a quantitative step in applications. You just can't do this stuff on an [Intel] 8088, and it's doubtful on a [Motorola] 68000: the hefty calculations of landscape perspective and particle motion for each scene need to be performed in less than the screen refresh period or the illusion collapses."
Graphics
Here, though, the illusion was maintained, all thanks to the power of the ARM. It contained 27 32-bit registers and could handle 44 instructions, the majority of which excuted in a single clock cycle. The CPU ran at 8MHz. It was attached to separate memory, video and I/O controllers, all designed by Acorn. The I/O chip was codenamed 'Albion'.
The VIDC – codenamed 'Arabella' and designed, like the other ARM auxiliary chips, by Tudor Brown, Mike Muller and others – supported colour resolutions of up to 640 x 512 – 16 colours; if you wanted 256, you had to drop to 640 x 256 – but could reach 1024 x 1024 if you were happy to adopt a single colour. It also handled sound output.
Inside the Archimedes A440
Source: Chris' Acorns
Novelly, the MEMC memory controller – 'Anna' – was able to support 32MB of memory – far more than it was economically feasible to add, so it was able to page the 4MB of physical Ram on and off a hard drive to provide rudimentary virtual memory, something we take for granted today. Ditto the application memory protection, a feature modern multitasking operating systems manage for their users.
Back then, the Archimedes' OS was called Arthur, only renamed RiscOS the following year, allegedly to avoid confusion with the movie Arthur 2: On the Rocks, also released in 1988, though this seems very unlikely.
Arthur is said to have stood for "A Risc operating system before THURsday".
Next page: Arthur
COMMENTS
Some comments from the Project Manager.....
HI. I thought I would provide a bit of feedback having been in the middle of it all at the time at Acorn. First a great article and factually pretty near the mark. Yes, Arthur 0.2 was in EPROM and we thought we would have them back as they were expensive and possibly re-useable. We set a very firm date for the launch, June 1987 if I remember and hence the OS was whatever state it had reached; not an ideal approach but it would have been sad to have left the superb hardware waiting for too long. Were Acorn products over-priced? No, the profit margin was reasonable bearing in mind the high level of R&D and the high technology. PC clones at the time were sold at very tight margins and made in the Far East or under railway arches in the UK with virtually no R&D spend as a result of the vast volumes. When I look back at Acorn Marketing it was some of the best I have ever come across in my career both before and after. Acorn made the best of being a niche player and inevitably struggled just as Apple did for a long time. Someone comments that Archimedes had 'Windows emulation'. No it didn't, it had genuine MS-DOS licences provided by Microsoft. It was the hardware that needed some emulation as many PC applications at the time wrote directly to the PC hardware bypassing MS-DOS much of the time (it was just a Disk Operating System after all not a Machine Operating System as in Acorn products). Finally as someone else has commented acronyms should always be in upper-case so it should be ROM not Rom etc. Why UK journalism insists on treating acronyms in this way when the USA gets it right is beyond me; it makes speed scanning of technical articles more difficult as I always scan for the techno words. So when RISC-OS was developed and launched it was all upper-case and never anything else; rant over :-)
Some factual errors
There are even more rabid fanboys than I in the RISC OS world, so I'll preempt them (or maybe just warm them up) with a few points:
"Risc", as you point out, is an acronym. Thus it should be RISC. Ditto "RiscOS", which should also be two words: RISC OS. "Rom" should be ROM. Confusingly, the last Acorn machine was the RiscPC (in lower case), but the official logotype has a sort of half-space, so most people write is all joined up as I do. Finally, the mouse buttons on an Acorn machine were referred to as Select, Menu and... Adjust, not "Alter".
There seems to be some confusion about the difference between Lander and Zarch: the former was a demo of the latter. The demo (Lander) shipped with most machines in this era, while the game (Zarch) was a commercial full product. It was exactly the same game on the PC, but known as Virus. The player's ship in that was not triangular (it was non-symmetrically pentagonal), and is the same shape as the Copperhead ship from Bell and Braben's game Elite.
Two final points. First: "Archimedes morphed into the Risc PC line, a series of ARM-based boxes designed to run Windows – on a co-processor, and presented in a Risc OS window." No. Just no. The RISC PC was never *designed* to run Windows - it was designed to run RISC OS natively, and use hardware-based emulation to run Windows within RISC OS. The "co-processor" wasn't a true one in the sense you seem to be inferring; the primary CPU was an ARM610, 710 or some variant of the StrongARM processor, while the secondary CPU was a specially designed 4x86 or 5x86 card which could *only* be used by the emulated copy of Windows. It was also not a default item included with the RiscPC, but usually a seperate purchase.
Finally, there's the fact that you say the line stopped with the death of Acorn/Element 14, without mentioning anything about the two spin-off companies RISC OS Ltd or Castle Ltd. Acorn's demise left RISC OS at 4.02, and ROL/CTL developed this further in two confusingly-numbered parallel brances, known as RISC OS 5 and RISC OS 6 (also known under the names RISC OS Select and RISC OS Adjust). There were also the the Iyonix, the Omega, and some other hardware designed and sold in the post-Acorn era. And last but not least, there are ongoing efforts to port RISC OS to small boards like the BeagleBoard and the Raspberry Pi, these mostly happening through RISC OS Open Ltd (ROOL), a spin-off created when Castle decided to open parts of the RISC OS source.
As an Acorn fan girl...
I loved my BBC micro. The first affordable ARM machine was the Acorn A3000. So I got that when it came out. By then I'd already been programming ARM code on a Uni Archimedes 305. I've known ARM assembler for almost 25 years. I feel old!
I still have my A3000 (plus a spare for parts) and my RiscPC which I replaced it (with a couple of spares including one which was an ex Acorn development machine). My RiscPC had the 486 card, 4MB RAM, 2MB VRAM and a 130MB SCSI HD. Alas the HD has died.
Basically those machines founded my career. On the A3000 I developed my first piece of commercial software. I produced an ARM Linux distribution for them in the 90s. I am now a software consultant and my work still requires me to do ARM dev. Finally to go full circle my Raspberry Pi turned up this morning. I will be putting RISC OS on it to play with.
Memories...
Remember these fondly when I was at school. Hours and Hours of playing Moonquake with my mates during lunch breaks. Soon as a teacher walked in, they were greeted with 10 resetting Acorns (CTRL+Break) followed by that "BOOOP" noise it makes on reset! Good times...
