Intel AMT [PSARC/2007/601 Self Review

[David Chieu]

Garrett D'Amore wrote:

> Paul Jakma wrote:
>
>> On Wed, 17 Oct 2007, Garrett D'Amore wrote:
>>
>>> I think this is only true when the host operating system is not 
>>> running. If the host OS is running, then gigabit should be fine.
>>
>>
>> So what happens when the host OS stops running suddenly (crash or 
>> hardware fault)?
>
>
> The AMT firmware is supposed to figure this out. I think the NIC drops 
> down to 100Mbps mode. I'm not sure exactly how this monitoring is 
> done. I imagine there is a watchdog register that is tickled or somesuch.

There is a separate ARC processor at the North Bridge of the PC 
motherboard. This processor runs AMT which can act like a watchdog to 
monitor the host OS.

>>
>> Further, it seems the host OS needs to re-enable the ARP intercept in 
>> the NIC hardware on shutdown. I'm very curious if that means a sudden 
>> host stop will render the AMT LOM inaccessible in short order..
>
>
> No, AMT is precisely designed the way it is to deal with this case. If 
> you crash your operating system, within a second or two (or 
> thereabouts) AMT figures out that the host is out to lunch, and the ME 
> takes over.
>
> In case anyone is curious, the ME/AMT environment is really like an 
> embedded service processor, and as such, traffic to it is probably not 
> terribly common. It has a serial port/console shunt, and also provides 
> some other features like remote host reset capability, etc.
>
In addition, there is a non-volatile memory area, in case of host OS 
crash, "the last words" can be saved there for postmortem.

-- David Chieu

> -- Garrett
>