RISC OS for the Raspberry Pi released | Hacker News Reader

RISC OS for the Raspberry Pi released

riscosopen.org

65 pointszdw28 comments

Why this is interesting:

"RISC OS is a fast, light-weight operating system specifically designed for the ARM architecture. It was developed by the same team of engineers who created the original ARM processor"

Original Acorn Archimedes (which ran RISC OS): 1988, £1000

Raspberry Pi: 2012, £27

Too bad Rasperry Pi didn't start on an ARMv7 Cortex A5 at least. So much effort being put into a near-death ARMv6 architecture.

Near-death? ARMv5 is still going strong, I'm pretty sure there's a decent amount of v4 being produced, too.

for those that would like to play, raspberrypi.org has a mirror with the latest-to-release RC5: http://downloads.raspberrypi.org/images/riscos/riscos-2012-1...

Site is down, how compatible will this be with the existing software library? If I'm not mistaken there was a pretty good set of Amiga/Atari ST games ported to the Archimedes back in the day.

Google cache version: http://webcache.googleusercontent.com/search?q=cache:ZIAA_ur...

Back in the day, a lot of those games made a lot of assumptions about the hardware that it directly accessed. Even going from ARM 2 to ARM 3 to StrongARM caused a lot of problems for games.

When I was writing games for the Archimedes, I was using ARM-assembly routines to write pixels directly to the double-buffered screen memory. So I think a full blown emulator would be needed, rather than just the same OS. Unless ARM-6 can still execute ARM-1 assembly, and it still has addressable screen memory?

Depending on what the MMU would allow (I know so very little about low level ARM) you could probably map an area of ram to the same address as the old screen memory and make a compatibility layer. This still assumes that ARM-1 is binary compatible otherwise. So you might be able to get some kind of help from the hardware for at least video, but I have no idea about sound and input. I believe that this kind of remapping should be doable in linux so I'd assume that it could be made into a layer in RISC OS also.

ARMv5 dropped support for the 26-bit-addressing mode back-compatibility, so v5 and above definitely can't run ARM1/ARM2 binaries. (Even in v4 the back-compat support was optional.)

RISC OS and most applications are now 32-bit OK.

If you used the OS-provided SWIs to get the base address of the screen memory, OS_ReadVduVariables for 148 IIRC, and similarly use SWIs to wait for the VSync and switch buffers then I'd have thought it works just fine.

The Archimedes had ARM 2 BTW, ARM 1 was just in the Tube co-processor for the BBC B. Some instructions are different with the RasPi, mainly to do with the PC register no longer having bits spare for Negative, Carry, etc. http://www.heyrick.co.uk/assembler/32bit.html has more details. There are external programs that detect and trap old 26-bit instructions when on 32-bit RO and allow old games to run but I know little about them; my last Acorn ARM machine was their R140 running RISC iX (a BSD port).

Its kind of sweet how this HN post flattened their server. I don't think RISC-OS has attracted this much attention for 25 years.

This is the final inducement for me to buy a whole stack of the things. Having owned a BBC Micro as a kid, I cut my professional teeth on ARM assembler for RISC OS and it remains to this day my favourite instruction set of all time: everything that was necessary & sufficient wrapped in a neat little orthogonally conditional package, and RISC OS was the elegant icing on that cake.

I don't even know what I'll use them for yet. I'll just sit down and play with it, like being 16 again.

uh oh, if it run's http://en.wikipedia.org/wiki/Zarch then goodbye free time :)

Awesome. As someone who spent 10 years with RISC OS, this just rocks.

10 years ago is very late in the RISC OS lifecycle, so I'm curious -- how did you come to discover it then?

I didn't read the grandparent as meaning "the past ten years" but "ten years at some point in the past".

That is correct. 1987 - 1997...

Ah, yes, my brain inserted "the last" in there somehow.

having always been mildly regretful at having missed out on the archimedes (jumped from bbc b to x86), this sounds like a wonderful thing to explore.

It was pretty good but not as good as the beeb was so you didn't miss out on a lot. The architecture was a lot more complex.

I thought the architecture was sublime. ARM / RISC-OS development was a joy.

It was until the riscpc and a5000 machines.

I'm suspecting the site is getting a bit of a bandwidth issue, but there are emulators to emulate the old archimedes, Atari and IIRC the amiga.

Various people have been testing old style games on the Pi so you guys might lose a bit of free time :-)

Which RISC OS version?

RISC OS version 5.17

RC5 is actually a released version, so the link above contains the most recent code. More links can be found on he forum: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=55&t=2...

Loved using RISC OS back in the day at school

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