> Me and Maki have hit a dead end in our work.  Basically, we are
> seeing clock interrupts (INT4) *before* the clock is being enabled
> by initclock().  This is what's causing _splnone() to hang in
> cpu_configure().  When it enables all interrupts, so many clock
> interrupts have been queued up as to overflow and hang the kernel.

Hmmm.
Maybe..., not only R4030_SYS_EXT_IMASK, but also R4030_SYS_IT_STAT
might work differently in the Magnum 4000SC.
If so, pica/picabus.c:pica_clkintr() cannot clear clock interrupt,
and this describes the reason why clock interrupts hang the kernel.
--
soda