From 7f92f23316e2997f6f2a515343cf2e7ca6249482 Mon Sep 17 00:00:00 2001 From: Edward Tomasz Napierala Date: Fri, 30 Nov 2018 15:52:03 +0000 Subject: [PATCH] Revert r341337; according to imp@ we still support these. MFC after: 2 weeks Sponsored by: DARPA, AFRL --- share/man/man4/ddb.4 | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/share/man/man4/ddb.4 b/share/man/man4/ddb.4 index 1bcb1ad653b7..972e77416fba 100644 --- a/share/man/man4/ddb.4 +++ b/share/man/man4/ddb.4 @@ -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