I swapped a 2687W v2 CPU into my nMP and it boots just fine. This is an 8-core CPU with 3.4GHz base clock, with up to 4.0GHz turbo on a single core and 3.6GHz turbo on all cores. 150W TDP. 1680 v2, the 8-core CPU Apple sells with the 2013 Mac Pro is only 3.0GHz base clock, with 3.9GHz turbo on a single core and 3.4GHz turbo on all cores. 130W TDP. Any suggestions for how to best stress-test my Mac Pro to ensure that a 150W TDP CPU can be used 24/7, even with GPUs stressed to the max?