Subject: Re: CCL:Linux on PowerPC

From: Rick Venable <[email-masked]>
Date: Fri, 20 Apr 2001 18:03:49 -0400

Perhaps there's a discrepancy, perhaps not; see the note below from
Cristoph regarding compilers.

The main problem with getting good performance under Linux for PPC has
been that the GNU compilers (gcc, g77) were optimized for Intel, and
produce code that runs very poorly under ppclinux or mklinux.  Now that
OSX has been formally released, one hopes that affordable, true native
compilers might become available for Linux kernels on Mac PPC systems.

If the SPEC benchmarks cited below were done with gcc, they do not
indicate the machine speed as much as the lack of architecture dependent
optimization in the GNU compilers.

On Thu, 19 Apr 2001, Joerg Grunenberg wrote:
> Here are some more benchmarks pointing to a discrepancy between reality
> and advertisement:
> 
> Processor               SPECint95               SPECfp95
> PowerPC G3(450 MHz)     21.4                    13.8
> PowerPC G4(450 MHz)     21.4                    20.4
> (" ...processing speed of a supercomputer..." ; www.apple.com)
> 
> Athlon (1.0GHz)         42.0                    29.4
> Pentium III (1.0GHz)    46.8                    32.2
> Alpha (833 MHz)21264A   49.4                    95.6
>  
> -- 
> Dr. Jörg Grunenberg, Org. Chemie, Hagenring 30, 38106 Braunschweig
> email: [email-masked] phone: +49 531 391 5252 
> URL: http://www.tu-bs.de/institute/org-chem/grunenberg/grunenberg.html

> > Yubo Fan wrote:
> > >computers can run Linux OS. PowerPC processor is much more powerful than
> > >PC chips in scientific calculations, at least Apple's ads said so. My
> > >question is: Can G98 run on SuSe Linux-Apple combination?
> 
> Christoph van Wüllen:
> > This depends on the quality of the compiler. My timings for a small
> > TURBOMOLE test suite are
> > 
> > Mac/g77       (29. 08. 99)   532 user  37 sys 0:10 real             G3 400 MHz
> > unibo13/g77   (22. 09. 99)   445 user  28 sys 0:41 real           Piii 500 MHz
> > CvW/PGI       (28. 09. 99)   320 user  16 sys 0:06 real           Piii 500 MHz
> > Gadolinium    (30. 03. 01)   178 user  29 sys 0:04 real           Piii 850 MHz
> > Achilleus/PGI (29. 03. 01)   161 user  11 sys 0:03 real         Athlon 900 MHz
> > 
> > That is, a G3 and Pentium-iii are similar at the same clock speed. The PGI
> > compiler for pentium gives 30 percent, and modern PCs at 900 MHz outperform
> > a G3-400 MHz by a factor of 3.3. Unless you have a FORTRAN compiler that
> > exploits the new G4 architecture, I cannot see why a PowerPC should be faster
> > than a Pentium. I love my Macintosh on my desk, but for doing computations....
> > 
> > --
> > +---------------------------------+-------------------------------------+
> > | Prof. Christoph van Wullen      | Tele-Phone (+49) (0)30 314 27870    |
> > | Technische Universitat Sekr. C3 | Tele-Fax   (+49) (0)30 314 23727    |
> > | Strasse des 17. Juni 135        | eMail                               |
> > | D-10623 Berlin, Germany         | [email-masked]    |
> > +---------------------------------+-------------------------------------+

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Rick Venable
FDA/CBER/OVRR Biophysics Lab
1401 Rockville Pike    HFM-419
Rockville, MD  20852-1448  U.S.A.
(301) 496-1905   [email-masked]
ALT email:  [email-masked]
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