MacRumors reports Restoring a Bricked iMac Pro Requires a Second Mac and Configurator 2:
"If an iMac Pro becomes unresponsive and requires restoring, like if there's a power failure during a software update, there are a special set of instructions iMac Pro users must follow, which require a secondary Mac."
As outlined in an Apple Configurator 2 support page, an iMac Pro restore requires a second Mac running macOS High Sierra with internet access and Apple Configurator 2.6 or later installed.
[...] This restore process is similar to what must be done for an iPhone or iPad that is unresponsive, and it is necessary due to the extra security afforded by the Apple-designed T2 chip ... [which] integrates the system management controller, image signal processor for the camera, audio controller, SSD controller, a Secure Enclave, and a hardware encryption engine.
(Score: 0) by Anonymous Coward on Monday December 18 2017, @08:32AM
- Connect a JTAG debugger.
Usually things are still considered bricked even when they can be unbricked with a JTAG debugger.