I have a Dell Precision T7500 work station. There are two intel xeon processors which show up as 12 CPU cores in the resource manager, numbered 0 through 11. When I export a Premiere project to AME, it only uses one core, number 1. 0 and 2 through 11 are untouched. This makes rendering very, very slow. This was not the case in AME CC6, which spread the load across the 12 cores and was much faster.
I read on another thread that this was a known bug in CC2014, but had been fixed in CC2015. However, I never used CC2014 and have this problem.
I have read other threads recommending launching AME before Premiere, or restarting the computer before doing the render. These have no effect on the problem.