doc/platform/kgpe/notes.md: mention watchdogs

doc/platform/kgpe/notes.md

@@ -20,3 +20,22 @@ PCI: 00:14.1 20 <- [0x0000003010 - 0x000000301f] size 0x00000010 gran 0x04 io
 PCI: 00:14.2 10 <- [0x00f0404000 - 0x00f0407fff] size 0x00004000 gran 0x0e mem64
 PCI: 00:14.3 a0 <- [0x00f0410000 - 0x00f0410000] size 0x00000001 gran 0x00 mem
 ```
+
+## watchdogs
+
+The KGPE-D16 has *at least* three separate hardware watchdogs!
+
+- One in the SB700 southbridge, although it appears to be disabled
+  (Linux's `sp5100_tco` reports that it cannot be enabled).
+
+- One in the W83795 hardware monitor (thermal/fan control chip)
+
+- One in the W83667HG-A SuperIO chip
+
+I've found the third one to be most reliable.  The Linux
+`w83627hf_wdt` kernel module for this watchdog works correctly, and
+I was able to write a coreboot patch (to be included with ownerboot)
+to start the watchdog extremely early in the boot process -- before
+DRAM initialization or PNP enumeration.  This is extremely helpful
+with unattended servers, where a hang in the boot process requires
+manual power-cycling.