> I've just done several tests on my Magnum, based on the odd behavior that
> enabling SYSCALL_DEBUG typically allows a successful boot to a single-user
> shell.  Testing the theory of introduced latency, I've inserted DELAY calls
> as high as 1 second where scdebug_call and scdebug_ret would be called from
> arch/mips/mips/syscall.c.  The tests were unsuccessful.  It would seem the
> sheer latency introduced by SYSCALL_DEBUG does not account for the successful
> booting.  It may prove to be more of a memory issue than one of timing.
> It's hard to say right now.

Cache issue?  Inserting SYSCALL_DEBUG code paths alters and bumps out
(stale) cache entries in effect.  Can you see any good/poor behaviour
difference to force R4000 to have write-thru pages?

#undef	MIPS3_PG_CACHED
#define	MIPS3_PG_CACHED 0x0

Tohru Nishimura