[Discuss] Kernel interpretation of pressing the reset button?

[Darren Duncan]

On 2018-06-12 7:55 PM, Alan W. Irwin wrote:
> So that leads back to the original question of why on some occasions
> when the kernel was locked up there was no response to pressing the
> reset button on this new computer.  Cy previously suggested a hardware
> fault was the cause of those intermittent failures of the reset
> button, and of the many possibilities there, your suggestion that the
> reset button might be jammed is consistent with my experience which it
> is it almost always something really simple that is wrong with
> computers.  :-)

All this discussion and no one has yet even mentioned that modern computers for 
at least the last 15-20 years or so have a separate piece of hardware that 
handles interpretation of the power button, including the reset functionality, 
among other things, called the PMU / Power Management Unit.

So really, it shouldn't matter if the kernel is locked up, the reset 
functionality can fallback to independent hardware, so there is a reliable way 
to reset hardware that's better than pulling the plug or battery and doesn't 
depend on any installed software.

https://en.wikipedia.org/wiki/Power_Management_Unit

On all the computers I've used for a long time, holding down the power button 
for like 4+ seconds performs a reset, where pressing and letting it go, or 
holding it only for a shorter time, will signal the OS.

-- Darren Duncan