What is the exected behavior with the NMI button?

[Sean Bruno]

While trying to get a deadlock sorted out in the GPROF code, I attempted
to use this fancy shmancy NMI button on my Dell server.

I noted that, not unlike the goggles, it did nothing once the system was
deadlocked.  I noted that when the system was running normally, an NMI
log message would be spewed to the console.

What is supposed to happen in these two cases when we toggle the NMI
button?

Sean