There are a number of threads already discussing options for this, although I definitely wouldn’t jumpstart a motherboard as the inrush current could damage the board and there’s also a potential fire hazard. As @kraegd mentioned Most PCs these days can do “wake on LAN” or WOL, which would be the preferred method.
You can see how other people have done this by looking at the “power” quick browse list in the community – created wiki in the project reports section. Just be aware that prior to June 2016 the SmartThings hub could not itself issue the WOL command, so you’ll see a lot of earlier projects that use a raspberry pi as an intermediary device just to issue the WOL command. After June 2016, you could just do it with a smart app, including Core. 
Or jump straight to the discussion of the official capability.