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Work starts on a RISC OS 5 ARM Cortex port

Published: 22nd Jan 2009, 19:06:54 | Permalink | Printable

An attempt to port RISC OS Open's flavour of RISC OS 5 to the Pandora, a 450MHz ARM Cortex-A8-powered ultra-portable net book, is underway, according to programmer Jeffrey Lee.

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This sounds very promising. I like the idea of supporting an ARM-powered device. Are they in fact available to buy though?

 is a RISC OS UserAW on 22/1/09 7:21PM
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Good luck Jeffrey - a very interesting project. Let's hope it bears some fruit. As he says on the ROOL forums, even if it isn't successful, the work should help to create a more portable RO5 in the long term.

 is a RISC OS Userlym on 22/1/09 8:11PM
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The Pandora website is rather out of date and it's not clear what the supply situation is. However, there's no need to wait for that before porting to the TI OMAP-3530 (the processor in the Pandora). There's the emulator qemu-omap which is free, plus a number of evaluation/development boards.

The best-known development board is the "Beagle Board" which is definitely available right now for the surprisgly low price of £100 - you don't get a case, but at least you get your own choice of keyboard (I'm not convinced by Pandora's).

I've been watching some demos of the OMAP3530 today as it happens, and I have to say it's a seriously impressive chip, and I can't see any show-stoppers that would prevent the majority of 32-bit RISC OS software from running on it. The only major omission I'm aware of is an Ethernet MAC, and that's promised for new chip variants out later this year.

At £100, I for one am seriously tempted to get a Beagle Board and start helping out with the port.

 is a RISC OS Userbavison on 22/1/09 9:05PM
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Chris, I think youre title is completely wrong, It should say work on Cortex8 HAL started, not RO5 port for Pandora.

 is a RISC OS Userhighlandcattle on 22/1/09 10:17PM
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I've got a couple of BeagleBoards in work if anyone's wanting builds testing. :-)

 is a RISC OS Userspanners on 22/1/09 10:44PM
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spanners: "I've got a couple of BeagleBoards in work..."

Have you tried connecting the DVI-D port to a normal TV's HDMI port and got it to work at all?

 is a RISC OS UserStoppers on 2/2/09 8:04AM
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As I explained in the ROOL forum thread that Drobe linked to, the Cortex A8 is just a processor core. The HAL abstracts peripherals, not cores; a Cortex A8 HAL would be equivalent to saying there's an ARM7 HAL, a StrongARM HAL, an ARM9 HAL and an XScale HAL (which there aren't).

Much of the porting work required is in the HAL - interrupts, timers, DMA, framebufers, I/O drivers, but some important work would need doing elsewhere. The kernel needs support for the changes to cacheing and page tables (the Cortex A8 has a L2 cache), and possibly an abort handler for unaligned loads and stores so that they work the way RISC OS software expects. The BASIC assembler and the Debugger disassembler need support for the new instructions. And so on.

There are some things that I'd not describe as a port, since they haven't existed before and so need to be written largely from scratch. For example, modules need to be written to interface to the HAL entries for SD card controllers, camera interfaces etc. An interface needs to be designed to the 2D and 3D graphics acceleration core. An interface to the (closed source) video DSP coprocessor codecs needs to be written (possibly by resurrecting and finishing off PRISM).

I'd agree that it's questionable to describe it as a port for the Pandora, because all platforms based upon the OMAP35xx chips are so similar. One good thing is that TI intend the OMAP35xx to be a general-purpose processor that will remain in production for years to come, finding use in multiple board designs, all of which we can then quickly support. This is in contrast to most ARM-based chips of recent years, which tend to have a very short shelf-life (many of them are designed for a specific customer for a specific product).

 is a RISC OS Userbavison on 22/1/09 10:53PM
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You mean apart from the S3C2440, as used in the A9 Home, which has been available for yonks and Samsung are commited to continuing to provide for yonks further?

 is a RISC OS Userrjek on 23/1/09 12:44AM
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I did say "most", not "all". :)

 is a RISC OS Userbavison on 23/1/09 9:19AM
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How will they cope the the lack of VGA output? (Only TV out.) Will they be putting one in? Will they be modding the hardware?

 is a RISC OS UserAnon on 23/1/09 2:24PM
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really? Pandora? it is a tiny thing mostly aimed a gaming.

There are some real nice netbook sized devices that are very portable and, for me anyway, would be more intresting.

A number of Chinease netbooks based around Samsung arm9 SOC's exist. Search for Jointech JL7100. (if it is the same chip as A9 can't remember but think it may be or a close varient) then this may be somthing that could be made to work a lot quicker and easier then a pandora.

Also we have netbook like devices coming (likely in next 5 months) with cortex CPU's from Freescale and Qualcomm (capable of 720p), nice screens and typeable keyboards. They will likely even come in cheaper than a pandora.


PS good luck though any work to understand optomising code for new ARM versions and working with porting will undoubtedly help with future devices.

 is a RISC OS Usermrmac on 23/1/09 2:41PM
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Sorry... not the jointech one.

See here for the Cuol Book which uses a 533Mhz Samsung S3C2440A and as the samsung chip is an SOC and the A9 already runs on one would it not be somthing we could have Risc OS working on very quickly?


also this is the same hardware; [link]

 is a RISC OS Usermrmac on 23/1/09 3:05PM
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Unfortunately, the CPU isn't the only bit of work to do. The A9 Home has a dedicated GPU, for which a lot of work was required to get it to work under RISC OS. While the 2440 has a built-in dumb framebuffer, it lacks hardware mouse pointer support (a bigger issue than it sounds), and even running at 640x480 is seriously saps memory bandwidth. I suspect this netbook also has a GPU (or just has poor performance) that would need drivers for RISC OS.

 is a RISC OS Userrjek on 23/1/09 4:52PM
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What GPU does A9 have?

Was only suggesting as CPU and a lot of the stuff that needed changed for A9 would be the same.

As you say though GPU work would be diffrent.

 is a RISC OS Usermrmac on 23/1/09 5:09PM
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Silicon Motion SM501. The other issue is that while the SoC's peripherals will all be the same, the memory map may be very different indeed; external peripherals (RAM, Flash, ethernet, etc etc) may (and most likely will) be in different places, with different timings, and different drivers needed.

All I'm saying is that it's not as easy as it sounds.

 is a RISC OS Userrjek on 23/1/09 5:22PM
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I'm not really interested in a Pandora port myself - as mrmac says the device is too small. What I'm really hoping for is that the Cortex-A8 SoC that's used in the Pandora will be the same as used in some of the ARM netbooks when they are released. Even if the chips aren't the same, this port will still be able to provide a good deal of groundwork for an ARM netbook port.

I hadn't heard of the Cuol Book before, but even if I had, I don't think I would have wanted to start porting RISC OS to it. Compared to the ARM netbooks that will (supposedly) be available soon, the Cuol Book will be a very underpowered device.

 is a RISC OS UserPhlamethrower on 23/1/09 10:33PM
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I really don't see much scope for an ARM in the netbook form factor of general purpose computers. This would place it squarely up against the Intel low power Atom family. There is only a small benefit in power consumption and cost from the processor when considering the system as a whole, and this is far outweighed by poorer performance and greatly reduced software availability. After a good start by Linux unfortunately it's now Windows shipping on the majority of devices, but just considering Linux the distros for the ARM are a lot poorer severed and even less ready for joe public to try to download new applications.

The ARM's niche is still in the ultra low power devices such as mobile phones, hand held game consoles and multi-media players, where software availability isn't an issue due to closed ecosystems, and power consumption accounts for everything. The Cortex doesn't have the horsepower to break out of this niche in to the general purpose world, indeed its needed just to stand still for the increasing sophistication of mobile applications.

 is a RISC OS Userdruck on 25/1/09 1:29PM
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However Riscos doesn't need (or can't expect) more power than these Cortex machines would offer at the moment.

If there is any hardware future for Riscos then this may well be it, and nowerdays it seems better to have a netbook than a desktop - if only because netbooks are exempt from the mockery that a 600mhz desktop would encourage.

 is a RISC OS UserMonty on 25/1/09 1:59PM
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I agree with that, but unfortunately no one is designing netbooks with RISC OS in mind. Any design would have to offer comparable experience running Linux applications to at least the current crop of 1st generation 900MHz Celeron and 2nd generation 1.6GHz Atom machines (similar performance despite the clock speed, the Atom having far better battery life). Keep in mind the 3rd generation featuring dual core Atoms for netbook class machines will be shipping in a couple of months.

 is a RISC OS Userdruck on 25/1/09 5:20PM
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They already are shipping. Also remember that these systems get shipped with very capable graphics accelerators, too. Certainly more capable than any GPU + drive combination RISC OS currently has.

 is a RISC OS Userrjek on 25/1/09 10:50PM
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The guys at TI openly admit that they're going head-to-head with the Atom and that performance is comparable. And I don't think that was including the grunt of the integrated DSP - for which many codecs (at HDTV level) are already available, including MPEG-2, H.263, MPEG-4, H.264, VC-1 (which encompasses Windows Media), RealVideo and VP6 - potentially these could all be made to work with RISC OS, and haven't we been crying out for that for years?

Maybe dual core Atoms are due out soon, but there are also multi-core Cortex-A9 chips in the pipeline too. Not that multi-core would be of any great benefit to RISC OS, of course.

 is a RISC OS Userbavison on 26/1/09 12:58AM
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Having used both CPUs, yes they are comparable. But comparable just means you can compare them :) The Atom chipset's bags faster, but more importantly runs more software.

Dual-core Atoms are already available (and still retain Hyperthreading, so they have four hardware threads).

 is a RISC OS Userrjek on 26/1/09 9:06AM
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More A8 hardware on the way... and look, the box next to the Efika2 board even resembles of another well known little blue box! ;)

 is a RISC OS UserRaeddie on 25/1/09 6:48PM
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I found this article quite interesting:


Whether there will be an ARM Netbook or Table from Apple is a good question but there are some strong arguments. Also it seems that the performance difference to the Atom processor is not so high.

However if there will be an Apple ARM Netbook it might be a good targat because the product live cycle seems to be a bit longer than that of other vendors. Also the Apple community is more open to alternative operating systems by default ;-)

 is a RISC OS Usermaikl on 25/1/09 9:25PM
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Just go for it.

 is a RISC OS UserAW on 25/1/09 9:29PM
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Ok here is some to check out we are looking at 1Ghz cortex A8's here;




Also these are just to give you an idea of some of the hardware coming up the qualcomm snapdragon above will have gprs/3g/hsdpa hardware which is low power enough to be always connected so you could have it collect emails for you when not powered up etc.

I think both of these chips are capable of 720p but obviously have a lot more horsepower than a 450mhz A8. There will be A9's and multicore versions of the CPU's available at some point in future but these first version are aiming for a retail release of mid 2009.

To give you an idea of other hardware that an oem has obviously made for mio the following prototype is the "Mio MID" which is an arm11 based machine (think somewhere about the 600-700mhz area). But apart from the usual it has GPS built in.

The only reason I mentioned the coulbook is they run a CPU which is already used (looking at the SOC spec from samsung it looks like the addresses for memory and lan etc would have a similar address). They are also cheap. If someone was buying in bulk they can be purchased from the OEM for under $100. This would make for a very cheap RISC OS portable. ie cheap enough for ex-users or users who have drifted towards other OS's to maybe have a little punt.

A lot of people had never seen any of those bits of hardware so I am not saying do this or the next thing. Just making the links available so people can see some of the upcoming arm hardware.


 is a RISC OS Usermrmac on 26/1/09 9:46AM
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