Features/ArchitectureSupport - changing what we build for

[Bill Nottingham]

Kevin Fenzi (kevin at scrye.com) said, in the FESCo meeting summary: 
> * Architecture Support
>   https://fedoraproject.org/wiki/Features/ArchitectureSupport
> 
>   FESCo tabled this to revisit this next week. There were questions
>   about OLPC support and LSTP client machines. Discussion to continue
>   on fedora-devel list.

As a followup to the discussion on compiler flags, this feature was
written up to describe a plan for what to do overall about what
architectures we support. The main points are:

- install x86_64 kernel on 32-bit OS where appropriate
- install PAE kernel on other 32-bit OS installs where appropriate
- build only i686 and above for Fedora

The last one is the issue that caused discussion during the FESCo
meeting. The main points raised:

- XO support

There is concern that building for i686 might break binaries on the XO.
The Geode on the XO self-reports as i586; this may need slight frobbing.
Aside from that, it "supports the i686 (Pentium Pro) instruction set, MMX,
the parts of SSE that do not involve SSE registers, 3DNow! Enhanced, a
couple Geode-specific instructions and a few SSE2 instructions." 
  (http://wiki.laptop.org/go/Geode_instruction_set)

This implies it should work; however, there have been bugs in the past
(https://bugzilla.redhat.com/show_bug.cgi?id=200330). Chris Ball stated
"my input as OLPC software dude is that we're probably okay with dropping
586, but it would be great if someone heled us test that everything's
looking okay first."

- K12Linux/thin client

Some older thin client hardware is not i686 compatible. Warren has more
info on this. One question I have is that some of this is mentioned
as being Geode - wouldn't this fall into the same category as the XO?
Also, just how much of this hardware is out there using Fedora now
(as oppposed to RHEL, CentOS, or some other distribution?)

More info is on the feature page. Note that in the smolt stats, i586
accounts for less than one twentieth of one percent of active systems,
an order of magnitude less than PowerPC.

Bill