Plain and simple: upgrade to the latest, if necessary, and compile with the flag:
Flashy and complicated: if you’re on CentOS5, specifically, you can do what I needed to do. I needed to write a patch for a client’s network of systems. You don’t need to do that, though, unless you need OpenMP on there (which you probably don’t). Wish I’d realized that was the issue before I went hog-wild.
So if you’re running into an issue where the ‘convert’ command is using 100% of your CPU (we had it running 800% — 100% x 8 cores), try the above. Most likely, that’ll fix ‘er.