[SunHELP] OpenBoot Parameters

[Greg]

> >           Wanted to know the difference between the parameters
> >auto-boot? and watchdog-reboot.

auto-boot? controls whether the machine boots automatically when power
is applied or simply stops at the OpenBoot prompt.

watchdog-reboot?, on machines that have it, controls whether the machine
reboots automatically if a watchdog reset occurs.  On SPARC v7 or v8
machines a watchdog reset occurs when code with traps disabled encounters an
exception.  Not much code runs with traps disabled and that code tends to be
very robust so a watchdog reset usually means there is a hardware problem
with a machine because the nested exception was unexpected.  If it happens
after recently changing the kernel in any way (kernel patches, new device
drivers) then suspect those changes before suspecting the hardware.

Watchdog resets on SPARC have nothing to do with timers or periodic checking
of the system, just a trap when traps are disabled.  watchdog-reboot? will
not enable any new code that runs or monitors the system, it only controls
the OpenBoot behaviour _after_ a watchdog reset occurs.

-greg