CPU utilization by processes

OS is HP
Number of CPU available is 4

I am running 8 multiple parallel application processes. I observed that the application is NOT able to occupy maximum CPU. Out of 4, 2 of them are used by 89% and 11% respectively. Where as other two are always sitting idle.

Can anyone please comment on why application is not able to use full CPU capacity?

regards

Are these separate processes or threads ? Do they interact at all ?
I would suggest using "tusc" to trace what they are doing ? Perhaps they are waiting on a common lock or waiting for I/O or something...

What version of HP-UX?
How are you displaying CPU usage and over what period of time? (sar, glance, top, other ?).
Does "ps" show significant CPU usage all the processes?
What type of HP-UX licence do you have? (see "uname -a").

What is the application? Are you sure it is multi-threaded?