>> So should I expect significantly better performance
with 5.3/smt ?

up to 30% with some applications

>>Now comparing that Power4 box with a shiny new p520 ( 1.5GHz Power5 )
>>the gain is a less-than-stellar 15%. From clock ratio alone I would
>>have expected 25%

i think you have answered your own question really. p5 are still dual
core the same as p4 .. p5+ however are quad core with larger on board
cache, so there will be some latency/access benefits to be had...

check out the rperf figures for each of the systems to see if they tie
in with what you are seeing..

Rgds
Mark Taylor