[Beowulf] Disappointing floating point performance for X5560 versus SPECmarks?

[Gerasimatos, Dimitrios V (343K)]

According to SPECfp2006, the X5560 should blow the doors off of the E5430.
The X5560 scores 36 while the E5430 scores about 18.


However, our own benchmarking using nbench, unixbench, and a home-grown
utility (twobod) all show that any differences are attributed to clock speed.


                X5560 at 2.80GHz         E5430 at 2.66GHz       X5560/E5430   X5560/E5430 at 2.80

    (twobod)
      time:         27.6 s               27.8 s              1.01             0.96

    (nbench)   
  FP INDEX:        34.294               30.767               1.11             1.06
 INT INDEX:        14.974               14.835               1.01             0.96

 (unixbench)
     SCORE:        1325.5                868.3               1.53             1.45
 reg. Dhry:         997.6                844.6               1.18             1.12
   DP Whet:         393.1                359.8               1.09             1.04


Has anyone else seen this? Any ideas to explain why this is? I am thinking of
going with the 3.2 Ghz version of the Harpertown chip clocked over the Nehalem-
based 5500 series.


Dimitri


--
Dimitrios Gerasimatos                     dimitrios.gerasimatos at jpl.nasa.gov
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