I compiled and run the loop test code posted by Otheus.

Xeon/SCO results: 555555.56 semop/s [0,0]
Xeon/Linux results: 128205.13 semop/s [0,0]

I don't have access to PIII box right now, but as results are same (proportionally) as what I saw in my test I think it is not crucial not to have PIII results here.

As far as overhead mentioned by Era - I am aware of it, as it is closely resembles situation that I am evaluating, so it a valid test and not an oversight.

So, does anyone have any idea what the bottleneck could be? or where to look? I really appreciate your patience with me and your persistence in getting to the bottom of it.