This would be because, given the workload, your external drive isn't quick enough to keep up with the CPU while your internal is? You could obviously use somet

This would be because, given the workload, your external drive isn't quick enough to keep up with the CPU while your internal is? You could obviously use something like nice / ionice if you don't want to kludge an external drive about, but to me it seems like an inherit problem with our systems that we can make them unusable just by doing something like a compile.