An enthusiast rummaging through firmware files for macOS High Sierra found information suggesting that the upcoming iMac Pro will be powered by server-grade Xeon processors and protected by an ARM chip known as a Security Enclave Processor. The existence of an ARM chip the same as those found in the MacBook Pro with TouchBar sparks speculation that the iMac may ship with a similar feature.
https://www.notebookcheck.net/iMac-Pro-may-pack-both-server-grade-Xeon-and-ARM-CPUs.230056.0.html