svn commit: r341342 - head/share/man/man4

[Edward Tomasz Napierala]

Author: trasz
Date: Fri Nov 30 15:52:03 2018
New Revision: 341342
URL: https://svnweb.freebsd.org/changeset/base/341342

Log:
  Revert r341337; according to imp@ we still support these.
  
  MFC after:	2 weeks
  Sponsored by:	DARPA, AFRL

Modified:
  head/share/man/man4/ddb.4

Modified: head/share/man/man4/ddb.4
==============================================================================
--- head/share/man/man4/ddb.4	Fri Nov 30 12:17:35 2018	(r341341)
+++ head/share/man/man4/ddb.4	Fri Nov 30 15:52:03 2018	(r341342)
@@ -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