[fedora-arm] ARMv7 rootfs/repository?

Chris Tyler chris at tylers.info
Wed Dec 22 14:30:13 UTC 2010

On Wed, 2010-12-22 at 14:19 +0000, Gordan Bobic wrote:
> Is there such a thing available? So far I have been working with a 
> Sheeva Plug which is ARMv5 (Marvell Kirkwood) based, so the armv5tel was 
> a good match.
> But this morning, my Genesi Efika Smartbook arrived in the post, which 
> is ARMv7 (Freescale i.MX515 Cortex-A8), and I think there might be 
> considerably more performance to be extracted from it if an ARMv7 
> compiled distro is used. I have found mentions of a F10 armv7l build for 
> a Beagle Board, but I was hoping for a more recent distro. Is there such 
> a thing available with a recent version of Fedora (ideally F12)? Or am I 
> going to have to build one myself?
> Thanks.
> Gordan

Hi Gordan,

There are two separate issues involved in going to armv7l from armv5tel
-- first, optimizing for the arm v7 architecture, and secondly,
switching from softfp (optional use of the FPU with fp function
arguments passed in CPU registers) to hardfp (mandatory use of the FPU
with fp function arguments passed in FPU registers).

I just recently got a report from a Seneca student studying the arm v5
vs. arm v7 (softfp) performance on a BeagleBoard xM, and his conclusion
was that there is little or no appreciable performance gain.

There is an expected performance gain with the switch to hardfp, but
that's a big challenge: you can't mix softfp and hardfp, so switching to
hardfp is like bootstrapping an entirely new architecture. The other
challenge is that the gcc used in Fedora does not yet support hardfp
with vfp; using another compiler might be possible, but could lead to
compatibility challenges with the primary arch.

Thus, my leaning is to hold off on the armv7l move until our gcc
provides arm v7 hardfp+vfp, which is probably F15 territory.


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