You may want to use sar, vmstat, top, or some other utility to determine what the bottleneck is on your system. My guess would be you are waiting on I/O to disk. You could increase your CPU usage slightly by using faster disks, although I doubt it is going to change your situation much. I don't do a lot of compiling but I am guessing it is a fairly I/O bound process and is probably bound to 1 CPU which means you will most likely never use both CPUs anywhere near 100% while compiling. If you don't have anything else running on the system, the CPU's are so much faster then anything else that unless you are doing some heavy crunching, the CPU will always be waiting for disk, memory, etc.