Multithreads run only on a single processor on a multiprocessor machine

I am trying to run external programs within a multi-thread Java program in an attempt to run the programs concurrently. It worked very well with some applications. Each thread started a separate external process on a different processor and run concurrently. However, it failed with the others. With these programs, the threads could start the external processes, however it seemed that all of the processes were running on the same processor and competing for that processor (the same process that Java runs on), resulting in a much slower performance than expected. The tests were done on a 32-processor SGI machine that runs IRIX64 6.5 and JavaVM-1.3. Does anyone get any idea about this?? Your help is greatly appreciated.
I have tried to use a shell script to get arround the problem. I have tried to start several processes (up to 8) from a shell script on the Unix command line. All of the background processes run concurrently on different processors and finished rather quickly. However, when I started the shell script from a Java program, the processes were sent to a single processor leaving the other processors in idle and all of the processes competed for the single processor where the JVM was running.
Does anyone have any idea what is going on? Thanks.
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I am confused.
Is the question about threads or processes? A thread
would be started with java.lang.Thread. A process
would be started with Runtime.exec(). And a script
file is only going to be relevant to a process. It
has nothing to do with a thread.I was wondering that as well, but I ignored what might be bad data and just took a stab at the most likely problem. No clue why the behavior with multiple processes should be as decribed - if so, it's definitely a very unlikely OS defect.
Chuck

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