Fans respond to load
How it tests
Reads the SMC fan speeds during the same 20 s load. For the load's last 10 s it raises each fan's minimum (applesmc's fanN_min; the SMC stays in charge) to halfway between its minimum and maximum, at least 800 rpm over its speed, never above its maximum less 100. The original minimum goes back on every way out; only a hard power-off mid-raise skips that.
How it decides
Supported: a raised fan went at least halfway to its new minimum (and 100 rpm or more), or a fan sped up 100 rpm under the load alone. Not tested (uncertain): fans steady, raise and all. Failed: no fans reported. Not tested (live limit) without the applesmc fix or the install kernel.
How sure it is
A fan that follows its raised minimum proves the fan and its reading, without waiting for the SMC to react to heat.
On a real Mac
- On a MacBook Air (13-inch, Mid 2012): minimum 2000 to 4200, the fan went 1996 to 4207, put back to 2000.
What could mislead it
- Could pass when it shouldn'tThe fan follows a raised minimum, but the SMC's own response to heat is broken (that lives in the SMC's firmware, the same under any OS).
- Could end without a verdictAn SMC that ignores the minimum leaves steady fans uncertain.