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Re: subarchitectures

Greetings, and thanks again for your feedback!

Adam C Powell IV <hazelsct@mit.edu> writes:

> Hello Camm,
> This is an important topic, and you've raised a lot of very interesting questions!
> Unfortunately, my last post exhausted my knowledge of the subject.  I refer you to my
> source, which is Ben Collins' post to debian-mentors a week or so ago:
> http://lists.debian.org/debian-mentors-0011/msg00230.html

Thanks for the reference!  I'll check it out.

> Camm Maguire wrote:
> > But fortunately, for
> > all cases you mention above except the k6,k7,p2,p3, code compiled on
> > one family (ev67, say) will run on ev4, though not optimally.
> I assumes this means there's no alpha asm involved?  If there were, you'd get illegal
> instruction errors running some ev6+ code on ev5s, etc.

Then I stand corrected.  Not knowing much about alpha, I assumed the
instruction set was compatible.  Goto-'s code is merged in the latest
atlas developer trees, so it appears the _alpha_ev? have to be added
to our problem list.  Do you know what minimum processor is required
to run Goto's code?

> > In the case we're discussing here, code compiled on p3 will not run on p2,k6,k7.
> > Argh.
> I guess this means there is some "Intel"-specific asm involved.
> In this case, has there been any mention of including some alpha asm in ATLAS?
> Kazushige Goto's work in this area runs substantially faster (on the order of 20-50%)
> than ccc-compiled ATLAS, and comes *extremely* close to the theoretical performance
> of the alpha.  It's all free, and available at
> ftp://www.netstat.ne.jp/pub/Linux/Linux-Alpha-JP/BLAS/ .

Thanks for the reference, see above.  Of course, one other solution
for now is simply to disable the improved code, compile a '386'
version for the distribution, and include a note for how the
interested user could build from source on his/her box.  This would be
a pity, it seems, and has the additional complication that the same
source tree needs to be instructed to build a general version on the
auto-builders, and an optimal version for the user.

Take care,

> -Adam P.
>                 Welcome to the best software in the world today cafe!
> --  
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Camm Maguire			     			camm@enhanced.com
"The earth is but one country, and mankind its citizens."  --  Baha'u'llah

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