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Revert r341337; according to imp@ we still support these.

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MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
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Edward Tomasz Napierala 2018-11-30 15:52:03 +00:00
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share/man/man4/ddb.4
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@ -1491,8 +1491,17 @@ might be defined to have special handling, and
might be defined to simply panic and reboot.
.El
.Sh HINTS
On machines with an ISA expansion bus, a simple NMI generation card can be
constructed by connecting a push button between the A01 and B01 (CHCHK# and
GND) card fingers.
Momentarily shorting these two fingers together may cause the bridge chipset to
generate an NMI, which causes the kernel to pass control to
.Nm .
Some bridge chipsets do not generate a NMI on CHCHK#, so your mileage may vary.
The NMI allows one to break into the debugger on a wedged machine to
diagnose problems.
Other bus' bridge chipsets may be able to generate NMI using bus specific
methods.
There are many PCI and PCIe add-in cards which can generate NMI for
debugging.
Modern server systems typically use IPMI to generate signals to enter the