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Author Topic: A new toy: The Raspberry Pi  (Read 2759 times)
pfft2001
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« on: January 15, 2012, 10:59:29 pm »

Happy New Year everyone!  Looks like I get the honor of the first post (on any of the OSD boards) of the year.

Read all about it at: www.raspberrypi.org

Looks really cool - price/size can't be beat.  I'm specifically looking at it as a "better media player" than the OSD.  Note that I really like the OSD for recording, but I prefer VLC for playback (see next thread).

Anyway, looks a nice toy - the question is to see if they can actually get it to market.
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heyrick
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« Reply #1 on: January 24, 2012, 11:50:30 pm »

Looks really cool - price/size can't be beat.

Indeed, it ought to ruffle a few feathers!


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I'm specifically looking at it as a "better media player" than the OSD.

Not here - I will be stuck with composite as it has no VGA output. However, for those with modern TVs, I think it would be pretty damn fine to play an HD XviD at full resolution.


Quote
Note that I really like the OSD for recording, but I prefer VLC for playback (see next thread).

I'm an SMPlayer man. Some of the recent fansubs have been some weird encoded MKV that only VLC will play, and it is nice to have VLC around as it copes with stuff that other programs choke on... however my heart sinks when I have to use VLC.

I find it amusing/ironic (in equal proportion) that my little eeePC running in overclock mode has an Intel Atom at 1.8GHz plus some graphics chipset, and it can *barely* hack H.264 video at 720p HD. Simple scenes are okay, but give it lots of motion and the display drops frames like crazy, slows down, stutters... the opening title sequence of "Fractale" damn near killed it [ http://www.youtube.com/watch?v=MMoRrvAeCjA ].

My little Xperia Mini Pro mobile phone (a mere 1GHz ARM with fancy GPU) takes 720p in its stride, is quite happy with it, and will softsub without hiccup. The only problem is being HVGA (320x480) it can be a little bit difficult to read hardsubs.

Enter the RPi, which is also HD capable. I heard somewhere it could do full (1080p) HD. Like, wow.


Quote
Anyway, looks a nice toy

Especially when the RISC OS port turns up. It'll be nice to run a native 32 bit
  • build instead of using emulators designed for the older 26 bit
  • version of the OS.
Quote
the question is to see if they can actually get it to market.

Considering that a lot of us thought it was vapourware when we saw the initial USB-pen concept, it has certainly leapt into the realms of reality. The question, for me, is if I can get my order in before the other fifty thousand geeks. I hope they limit initial sales so people don't say "yeah, I'll have a dozen".


Best wishes,

Rick.

* - while ARM has always been a 32 bit processor, the original ARMs used a nifty trick to hold the Program Counter and the Status Register in the same 32 bit register. Doing this left 24 bits for the execution address, but since the ARM is word aligned, that means effectively 26 bits (i.e. the bottom two bits of an address would be assumed to be zero). This is called 26 bit mode, or PC+PSR to make it clear. Problem is, 26 bits allows an addressing range of 64Mb. When the RiscPC arrived, with its ability to hold up to 256Mb RAM, it was STILL running in PC+PSR mode. You could use ALL of the RAM with some clever paging, but it had side effects like a single application was limited to a maximum of 28Mb (as the rest would be mapped to hardware/display, OS workspace, ROMs, module area, etc etc). It was a wicked hack, in both senses of the word. Smiley
Acorn, never one to forget the legacy of the BBC micro [US readers, think AppleII with added awesome] and bending over backwards to want to remain compatible to appease cash-strapped local education authorities (that's the accepted excuse, but since Acorn kit cost a lot more than comparable x86 boxen, I'd consider "lazy" to be a more realistic excuse), they remained firmly in the PC+PSR world. Even the cancelled Phoebe project was going to be Yet Another Rehash Of RISC OS 3-point-something. However after the demise of Acorn, ARM Ltd all but dumped legacy mode. Hell, even ARMLinux had gone 32 bit native by then. All you'll find now is a very very small chapter in the Architecture Reference Manuals, and they're a decade old...
Castle put together a computer called the Iyonix, which had a processor incapable of running in PC+PSR mode. This meant RISC OS had to be converted to 32 bit.
Now, given that the original APCS specified the called function saved/restored flags, and that you could restore registers, flags, and exit a function in one instruction ( LDMFD R13!, {Rx-Ry,PC}^ ), it must have been a HELL of a job to get RISC OS converted. Miss one '^' in a privileged mode, you'll find you've just dumped your registers into the user mode register set. Okay, in 99% of the times it won't matter much (extra shadowed registers are really only an issue in FIQ mode, plus often the processor flags aren't usually relied upon across function calls anyway), but you can't be lackadaisical as that way leads to random obscure crashes.
The Iyonix is dead (too expensive for RoHS certification), but their work lives on in the Armini, the Beagleboard, and soon to be the RaspberryPi. I have, also, a sort of (long) work in progress of writing a HAL to bring up the RISC OS kernel on the (original) OSD, just, you know, because. Wink

<cough> Sorry. Bored, waiting for Chihayafuru to download. FWIW, I'm the administrator of ARMwiki. It's fun to revisit old ground, but it's tedious rewriting it all again. Hehe...

Crappy old (like 15 years old!) ARM assembler stuff: http://www.heyrick.co.uk/assembler/
Awesome new sexy-wiki waï-waï-waï: http://www.heyrick.co.uk/armwiki/
RISC OS 5 (the 32 bit one), sort of open source: http://www.riscosopen.org/
Confirmed geek: uh... me. http://www.heyrick.co.uk/blog/
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pfft2001
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« Reply #2 on: April 03, 2012, 04:53:25 am »

FYI - there are still problems over in RPi-land.  Nobody (outsider of the inner circle) has yet to receive one.  They've had some, er, delays...
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heyrick
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« Reply #3 on: April 03, 2012, 08:09:27 am »

Ah, you're in as you now. Cheesy

Yes, something like that could have killed a less optimistic company. The thing RPi have going for them is that they are offering a spec not unlike a Beagle for about an eighth of the price.

Some have uncharitably said this is what you get when you outsource to China, others point to typical English mismanagement. Personally, I think it is a bit of both - from forum posts in early days, it seems the target price and main chip were the only clear decisions, the rest was sort of made up on the go...

...however the level of enthusiasm is still high. They want to sort the problems and get the things shipping. Soon.

Best wishes,

Rick.
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