FYI: Current SPECfp landscape...

Josip Loncaric josip at
Thu May 10 10:11:39 PDT 2001

We are also looking at the SPECfp2000 numbers like these:

Bob Drzyzgula wrote:
> Processor                   MHz  L2 KB SPi2K SPfp2K est core $
> -------------------------  ---- ------ ----- ------ ----------
> Pentium 4                  1500    256   536    558  2,100 (D850GB, RDRAM)
> AMD Athlon (Thunderbird)   1330    256   539    445  2,000 (GA7DX, DDR SDRAM)

Looking at the details of the SPEC tests, it seems that the compiler
plays a huge role.  Both machines ran Windows 2000 SP1.  The P4 result
used Intel's Fortran 5.0 (ifl), while the Athlon result used ifl for
some F77 code and Compaq Visual Fortran 6.5 for other F77 and F90 code.

Athlon vs. Pentium 4 benchmarks range all over the place.  SPECfp2000
has some CFD-like tests (swim, mgrid, applu, galgel).  The 1.7 GHz
Pentium 4 beats 1.33 GHz Athlon on F77 code, but loses on F90 code.  Per
GHz, the F77 P4 "win" factors are 1.25-1.59, while the F90 P4 "loss"
factor is

P4 should shine on codes where data is accessed sequentially with unit
stride.  Jumping around can lead to very inefficient use of the memory
bandwidth.  Also, optimization switches can make a huge difference. 
We'd like to test our own code compiled with our own compilers.  The
overall 2:1 performance uncertainty is too large to ignore.

For memory bandwidth limited code optimized for P4-friendly memory
access patterns, P4 should beat Athlon by about 50%.  This performance
gain matches the fact that PC2100 (DDR SDRAM) memory is currently about
40% cheaper than PC3200 (RDRAM) memory.  Unfortunately, we just do not
know how many codes fit into that P4-friendly category yet...


P.S.  This link has results of a CFD benchmark on a variety of
machines.  They report virtually identical P4 and Athlon performance on
the "per GHz" basis:

Dr. Josip Loncaric, Research Fellow               mailto:josip at
ICASE, Mail Stop 132C           PGP key at
NASA Langley Research Center             mailto:j.loncaric at
Hampton, VA 23681-2199, USA    Tel. +1 757 864-2192  Fax +1 757 864-6134

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