Hello Andrew,
> Le 22 sept. 2016 à 13:53, Andrew <ni...@seti.kr.ua> a écrit :
> Hi.
> On 22.09.2016 20:32, Jean-Roch Blais wrote:
>> Hello Andrew, Erich !
>>> Le 21 sept. 2016 à 04:52, Andrew <ni...@seti.kr.ua> a écrit :
>>> Most of boards have some kind of watchdog on board (in MIO or in south
>>> bridge), or some of them. For ex., iTCO_wdt for Intel, it87_wdt for ITE
>>> MIO, and so on.
>>> But built-in watchdog behavior may differ depending board model (it may
>>> reboot board, or it may just poweroff board, like ITE watchdog on old
>>> Asus K8N).
>>> Also, Intel watchdog driver is loaded automatically, MIO watchdog
>>> drivers are loaded manually (from command line or from /etc/modules).
>>> You can try it - load driver, and then do 'killall -9 watchdog' (to kill
>>> watchdog process & simulate system hangup). If board will be rebooted -
>>> all is OK.
>> Yes it does that indeed, I killed the watchdog0 and 1 plus the watchdog 
>> processes and my system rebooted, the drivers are already loaded in BUC ( 
>> lsmod gives iTCO_wdt ), no need to load anything, but it’s good to know how 
>> it works. But my question still stands, there is no hardware lockup watchdog 
>> timer, it has to be an external contraption which would detect an absence of 
>> activity on the motherboard and activate the hardware reset button… I’ve 
>> seen some wifi switches that do this for routers 
>> (https://www.amazon.com/gp/product/B01BU2ALGO/ for exemple).  It does not 
>> ship to Canada though :-) !!!  I’ve started some preliminary tests to 
>> perform the same basic thing using an Arduino on one of BUC’s USB port, and 
>> it looks promising… if you are interested I could let you know how it goes !
>> bye !
> You are wrong, iTCO_wdt is hardware watchdog timer. It doesn't use CPU for 
> rebooting - this is separate circuit in the chipset.
> You may even try to disable reboot on kernel panic and initiate kernel panic, 
> or even teke out one DIMM module - and system will be rebooted.

Ok I gladly agree to this, since this means there is no need to devise an 
external watchdog timer, right ? There is a lot of people who don’t know that 
then… :-(
My previous motherboard would not reboot when it hanged, this is why I thought 
there was no hardware wdt, but it might be that the wdt on this mobo only shuts 
down the mobo like you said before. ( it is a Foxconn 661MXPlus 
[img]http://i.imgur.com/38JiUW9.jpg[/img] and the SIS900 onboard nic was now 
and then sending me warning messages… ) So depending on the mobo, the wdt can 
reboot or shutdown the mobo, do you know any way to choose which  ???

thanks again !

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