> I'm running NetBSD 1.6W without any problems on a SPARCstation 20, dual
> SuperSPARC II 75 MHz, 8 x 32 MB SIMMs. I compiled a new kernel (tried both
> CVS from Sep 7 and from today), but it bails out on boot: "Level 15
> Interrupt" when using my old 1.6W-config and "Illegal Instruction" when using
> GENERIC.MP. However, the GENERIC.MP boots fine when it's stripped...

 I've also had periodic problems booting sparc64 kernels.  I'm not sure if I
saw the "Level 15" errors, but "Illegal Instruction" was common.  After some
off-list discussion with Manuel Bouyer he thought it might be an integer
overflow in the boot code, related to the disk blocks the kernel occupied.  He
asked me to send more details to port-sparc64 but I've been too busy with the
recent worm outbreaks to get my facts together.

 As a quick test, try making several copies of the "bad" kernels, and then try
to boot each one.  Do some work and not others?