[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: cortex / arm-hardfloat-linux-gnueabi (was Re: armelfp: new architecture name for an armel variant)

On Wed, Jul 14, 2010 at 5:21 PM, Lennart Sorensen
<lsorense@csclub.uwaterloo.ca> wrote:
> On Wed, Jul 14, 2010 at 05:11:16PM -0500, Matt Sealey wrote:
>> It's ARM's architecture and theirs to license, not Marvell's or Qualcomm's.
> Oh I hadn't realized cortex was an ARM name for that particular feature
> set.  In that case I can see how it makes lots of sense as the name.
> I for some stupid reason thought that was a product name of some ARM
> licensee.

It's not really a name for a feature set, so much as.. well.. If you
go grab a Cortex-A8 (i.e. a CPU) license you probably get as a job lot
the libraries to make an ARMv7-A CPU core, the VFPv3, NEON stuff. It's
part of the architecture in about the same way as AMD Vision is the
Athlon Neo line, and Intel Centrino is anything with
CPU/NB/SB/Wireless all from Intel. A brand that lets you know, these
features are in there somewhere and you can count on a certain level
of functionality within a limited subset of options. You can directly
compare Cortex-A8 "branded" processors from different vendors. This
helps ARM sell more licenses and gives companies like Genesi the
ultimate choice of silicon vendor based on the IP that the silicon
vendor adds and not the CPU core itself. We're solid on the fact that
the Cortex-A8 and Cortex-A9 are damn nice little CPUs... the choice is
in, what graphics is in there with it, does it support MS-CAN, how
many SPI buses.. :)

The other option is you go get an architecture license which lets you
go out and implement the instruction set with your own special
pipelines and bus interfaces to the cache and other bolt-ons like
custom SIMD units. You lose the ability to say it's a Cortex-A8 but
Freescale,  Samsung, TI (all cpu licensees) and Marvell, Qualcomm
(architecture licensees) have already spoken with 2 years of chips
that meet pretty much a standard set of requirements which you can
attribute to this grouping of features that ARM have dictated under
the banner of their Cortex-A8 brand even if they don't all use it. The
silicon vendors are tied in by what each other are doing and how they
can do as little software work as possible :) What a Debian port with
hard floating point ABI in use might spur (perhaps once all the
derivatives catch on, Ubuntu especially as they have their hooks in
commercial interests like Adobe) is greater adoption of a better base
level of CPU from ARM-licensee silicon vendors.

Yes, Marvell Armada 500 and 600 support a different armv7 core (it's
licensed but it's not Cortex-A, it's Sheeva P4J) and Qualcomm's
Scorpion core is on some kind of performance-enhancing drug, and even
Samsung/Intrinsity/Apple's A4 "Hummingbird" is Cortex-A8 with some
special power features and a speed bump but they don't advertise it as
ANYTHING (it's just a.. you can't please everyone's brand names or
feature sets, so we felt it's best to go up to the top level and ask,
what do ARM call this selection of features? They are all ARM
licensees so, they are in a common group and it does not pander to
individual silicon vendors (except perhaps those who took the Cortex
brand where it will be more obvious). Who will this benefit most?
Right this very second, all of them, with a little more emphasis on
ARM who get to make it look like all their processor designs are
suddenly 20-40% faster :)

In the end this port will not work on every plausible (even if never
produced) Cortex-A series variant. Some might not have an FPU - we
haven't seen one yet though. But it will work on some other compatible
architectures like Scorpion and Sheeva P4J and Hummingbird. This is a
matter for documentation in the same way armelhf would have to explain
what CPUs this actually encompasses (and what the difference is
between arm and armel in the first place). But it will support pretty
much everyone to the specifications we've recommended even if they
hate that they are not getting their brand name in there :)

Matt Sealey <matt@genesi-usa.com>
Product Development Analyst, Genesi USA, Inc.

Reply to: