As per title, I have a non-parallelizable script (numeric, not much IO) running in 6 separate MATLAB instances on a 16 CPU Xeon E5630. I figured these instances would all run fast however if I fire up another MATLAB and run bench(3) it indicates my machine is running just slightly better than an Intel Atom. I don't mean the graphics - FFTs, LU, sparse, etc. all are reporting poor numbers.
The RAM appears to be adequate (see output of "top" below) and overall CPU is at 39% utilization. There's nothing else heavy running on the machine. Maybe I have misunderstood how multi-core machines work!?