I asked previously a question about the maximum number of cores used under threadFor. The initial release of Gauss 15 could take at most 4 physical cores. Quoting Aptech, "Around the beginning of March, 2015 GAUSS version 15.1 will be released which will by default set the maximum number of threads to be the number of cores on the machine." So when will the new release come out? As of today (March 8), it is still 15.0.7.
A release candidate for version 15.1 is in final testing. I would expect it to be available within a week or so.