ia64 r255488: spontaneous reboots, no panic, no trace in logs

On r255488 ia64 I get spontaneous reboots,
which are more or less reproducible.
These are triggered by nginx serving poudriere built
packages.
The is no panic, and no traces in the logs.
The system just reboots.

A similar issue was seen in about 2011, when
we tried to build is64 packages on portscluster.
I think marcel_at_ gave up on it.

Has any new diagnostics been added since then?
Anything else I could try to see what is going
on prior to the reboot?

Thanks

Anton