HardOCP published some pics last week which show you how Intel tests the thermal performance of its processors. Apparently they don't trust on their own software, they drill a hardware monitor into the IHS:
When we concluded the first roundup of CPU heatsinks Kyle and I both came to the same conclusion. Software monitoring just isn't going to cut it. We need to step it up the [H]ard way. That is just what we did. We reached out to Intel about using a hardware monitor drilled into the IHS to measure the CPU temperature and wouldn't you know it, this is the exact way Intel tests their own chips. We knew we were on the right path.