5 ms·

Regarding Intel ME/AMT: how does it work when the computer is powered off? On a wired network, I imagine some system which stores the nearest switch's port con

Regarding Intel ME/AMT: how does it work when the computer is powered off? On a wired network, I imagine some system which stores the nearest switch's port connected to that machine, and you could send some sort of signal which powers things up. But even that seems, impossible? I guess it's not unlike hitting the power button; you're just sending an electrical signal to the computer which makes it start. The path of that signal is unimportant.

wmf 9y ago
The computer isn't off; the NIC is still on and it can wake the rest of the system. https://en.wikipedia.org/wiki/Wake-on-LAN https://en.wikipedia.org/wiki/Wake-on-LAN
dfox 9y ago
Regardless of AMT there is standard protocol to remotely wake computers over ethernet (since mid-90's or so). NIC that supports it can be powered from 5Vsb and in that mode listens for specially formatted ethernet frame (format is somewhat configurable, but by default it consists of several repetitions of NIC's MAC in payload, actual destination MAC is unimportant as long as the frame passes through configured receive filters) which causes it to pull down wire going into motherboard's power management logic (and thus causing the same thing as pressing power button). This usually has to be enabled by BIOS and thus does not work in S0 (as is the case for almost all wakeup sources except physical power button, which is usually wired such that it unconditionally shorts PSU's PS_ON wire to ground and does not need any software configuration to cause wakeup). Probably all onboard NICs support this and for PCI cards this requires additional cable between NIC and motherboard, PCIe includes required wires as pins B10 and B11 (with 3.3V instead of 5V and with active detection that inserted card is actually capable of generating wakeup events). If I correctly understand how AMT works then it implements it's own mechanism with similar purpose inside ME firmware, which with AMT enabled remains active even in S5.
myself248 9y ago
It doesn't need to be a wired network: https://software.intel.com/en-us/articles/technical-considerations-for-intel-amt-in-a-wireless-environment https://software.intel.com/en-us/articles/technical-consider...

wmf 9y ago

The computer isn't off; the NIC is still on and it can wake the rest of the system. https://en.wikipedia.org/wiki/Wake-on-LAN https://en.wikipedia.org/wiki/Wake-on-LAN

dfox 9y ago

Regardless of AMT there is standard protocol to remotely wake computers over ethernet (since mid-90's or so). NIC that supports it can be powered from 5Vsb and in that mode listens for specially formatted ethernet frame (format is somewhat configurable, but by default it consists of several repetitions of NIC's MAC in payload, actual destination MAC is unimportant as long as the frame passes through configured receive filters) which causes it to pull down wire going into motherboard's power management logic (and thus causing the same thing as pressing power button). This usually has to be enabled by BIOS and thus does not work in S0 (as is the case for almost all wakeup sources except physical power button, which is usually wired such that it unconditionally shorts PSU's PS_ON wire to ground and does not need any software configuration to cause wakeup). Probably all onboard NICs support this and for PCI cards this requires additional cable between NIC and motherboard, PCIe includes required wires as pins B10 and B11 (with 3.3V instead of 5V and with active detection that inserted card is actually capable of generating wakeup events). If I correctly understand how AMT works then it implements it's own mechanism with similar purpose inside ME firmware, which with AMT enabled remains active even in S5.

myself248 9y ago

It doesn't need to be a wired network: https://software.intel.com/en-us/articles/technical-considerations-for-intel-amt-in-a-wireless-environment https://software.intel.com/en-us/articles/technical-consider...