One thing you can try is: 1. download imagecfg.exe from http://www.robpol86.com/pages/imagecfg.php 2. run the command: imagecfg -a 0x1 link.exe This will set optlink to use only one core. I've suspected for a while that the multithreading locks in it don't work right for multicore. I have a single core machine and cannot test multicore behavior.