[fedora-arm] armv7hl requirements

[Peter Robinson]

On Fri, May 6, 2011 at 7:51 AM, Gordan Bobic <gordan at bobich.net> wrote:
> Matt Domsch wrote:
>> On Wed, May 04, 2011 at 01:46:06PM -0500, Jon Masters wrote:
>>> Folks,
>>>
>>> I'd like to kick off a discussion about flags for ARMv7. My proposal
>>> here is that we treat v7hl as an entirely different architecture, and
>>> don't try any multi-arch kind of hacks (there isn't the established user
>>> base for Fedora ARM to justify doing any of those things at the moment).
>>>
>>> Things I think we should consider as a minimum:
>>>
>>> *). Little endian (obviously, but worth stating) (l)
>>> *). Cortex-A8 or higher fully compliant core(s)
>>
>> Is there a measureable difference in code optimized for A8 vs A9 when
>> running on A9?  If so, my inclination would be to build for the future
>> - A9.  It's not like A9 hardware is hard to come by these days.
>
> I think the key thing to consider is cost/benefit. If the code optimized
> for A9 runs poorly on A8, but the code optimized for A8 runs on A9
> almost as well as the code optimized for the A9, then it would be better
> to optimize for the A8.
>
> Since A8 doesn't have OoOE, it wouldn't surprise me if latter was the
> case (A8 code running imperceptibly  worse on A9 but A9 code running
> much worse on A8).
>
> There is also the more philosophical issue - A9 is already faster than
> A8, so it may be better to target the A8 on the basis that it is more in
> need of that extra boost.
>
> Having said that, the only real hardware platforms that are likely to be
> affected here are the Genesi Efika and the Beagleboard. Everything else
> that is popular seems to be either ARMv5 (Sheeva/Guru plugs) or A9
> (AC100, Pandaboard, Trimslice).

Actually there's dozens of devices that use A8 processors. The Nokia
n900 and dozens of other phones. They may or may not be desirable to
support but there are a number of other tablet or netbook devices that
would be nice to be able to use.

Peter