Core Duet has failed and can’t restart.

This in turn can occur because of a bug in the SMC firmware.

The SMC needs to be reset, usually because of a software glitch.

A common reason for failure is damage when a user attempts to repair or upgrade their Mac. Unfortunately, as these are often embedded in hardware components, replacement may require a complete exchange logic board, or similar. Among the common reasons for failure are:

The fans themselves, and associated air ducts, grilles, etc.įailure in any part of that system can render the system non-functional, which should release the fans to run at maximum speed for safety.

The Core Duet software control system for energy management in macOS.

The System Management Controller (SMC), either a separate custom chip or part of Apple’s new T2 chip in some recent models, with its own firmware.Temperature sensors embedded in several or many parts of its hardware.The control system consists of the following components: When your Mac is hot and needs cooling down, which is exactly what the control system is intended to do, of course.When a kernel panic or other system failure is so severe that the normal control system stops working.When that Mac is in Target disk mode, in which the normal control system may be unavailable in some models.These include when the thermal control system is unavailable to slow its fans down, and are typically: There are circumstances in which your Mac’s fans may well be intended to run at their maximum. It’s the control system which slows them down from that, so long as your Mac stays cool, and the system is functioning normally. Macs are engineered for self-preservation: by default, their cooling fans are set to be full on, blasting away at maximum revs, to prevent your CPU, chipsets, and SSDs from overheating to death.

Normal temperature smc fan control