[Wien] processor cache / memory bus speed

[wiener at arcscluster.caltech.edu]

Dear Wien2k users,

We are currently looking into renewing our Linux beowulf cluster to run 
more Wien2k calculations. We would use Wien2k on cells containing up to 32 
atoms (transition metal alloys), and are interested in calculating 
the relaxation of atomic positions around impurities, as well as 
force-constants and elastic constants.

We are currently thinking of going with P4-3GHz machines (about 10 of 
those) with 1-2GB memory each and 100mb ethernet, but any suggestions are 
welcome. 
One of the questions we have in choosing our hardware is how much 
processor cache does the code use? Does Wien2k benefit from having a large 
processor cache of 1-2MB or is 512k sufficient? what is the speedup?
Also, has anyone done studies of the importance of memory bus speed?

Thanks in advance and regards,
Olivier.