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Re: [LUG] Java on Pi

 

On Thu, 14 Jun 2012, Rob Beard wrote:

I found a Netinstall image for the Raspberry Pi, I think it was an unofficial version of Debian which they call Raspbian. I've only just installed it on my Pi and not really had much chance to play with it (the install was fairly slow so I left it going) but maybe it might be a good option rather than to use the current images. I'm sure you'd maybe be able to advise Gordon, I'm not an expert on Debian so I don't know if what they've done is good or bad.

I run Raspbian and standard Debian in mine.

However...

And here you learn more about the ARM architecture and its instruction level support than you really want to know )-:

The ARM in the Pi is ARM architecture version 6

ARMv6 has hardware floating point.

However Debian don't consider it to be a "proper" hardware floating point processor because it's lacking some newer instructions, so it produced an release for it which has software floating point (armel). Debian requires ARMv7 before it properly supports hardware floating point.

Now... It's possible to compile programs for the ARMv6 to use the hardware floating point, BUT, the function calling ABI still uses integer registers to pass floating point arguments - in Debian armel. This is somewhat sub-optimal. Also all the userland programs that might need floating point are compiled to use software floating point.

So... A small number of individuals are producing a new Debian release from scratch (compiling it on Raspberry Pis and other ARM systems as Debian needs to be compiled natively apparently). This release uses hardware floating point by default and uses the newer armhf ABI for parameter passing...

It's based on Debian Wheezy (testing) rather than Squeeze (stable).

And yes, some aspects of it are much faster! I run xfce4 under it. There are still 1 or 2 issues to be solved though - e.g. the midori web browser crashes unless you turn javacript off, however the Pi is never going to be as capable as a "proper" desktop PC.

Make sure you get the rpi-update program and run it, although, I've compiled up my own kernel for mine just to give me 2MB more RAM - more important when you only have 224MB to play with!

Gordon

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