r270287: crash

FreeBSD r270287 crashes/reboots instantanously on loading the kernel. I
can not see at what point (on modern systems like Ivy Bridge). On older
Core2Duo systems I get a trap 12 in APIC or similar.

While I was able to start kernel.old on the modern systems, I fail on
both kernel and kernel.old on the C2D system.

I'd like to know whether there is a way to save the system I can not
reboot the on-disk kernels snce they are, woderfull, compromised.

Is there a possible scenario  like:

a) boot from DVD ROM or USB most recent snapshot
b) establish network with on-disk config, svn checkout recent sources
into on-disk file hierarchy
c) build repaired/patched kernel and install on on-disk (not on the
emergency boot media).

Thanks, help appreciated and what is about this crash affecting recent
CURRENT r270287, what has corrupted the system?

Regards,
Oliver