As this may become a closed circuit, so will it make my motherboard dead? or nothing will happen. How os will act on this internally?

  • why downvoted? I asked it because kids will find these cable easily and while playing they can connect it. – Ali786 Jul 9 '19 at 9:20
  • @MátéJuhász, true, how we can secure it so that it cannot happen? – Ali786 Jul 9 '19 at 9:22
  • @MátéJuhász not true. USB follows a standard, regardless of implementation. – LPChip Jul 9 '19 at 9:53

USB Specification states that before any power transfer or data transfer goes on, a handshake has to be approved first.

This basically means that when you connect the cable as suggested, the system itself will do 2 things: ask for a connection and receive a connection. Because it knows what kind of device it is, it is quite likely that it will do nothing at all. In either case, it will not send any current through the device that is strong enough to kill your device. If your laptop can be powered by an USB-C connection, then your laptop will also be protected by receiving that power from itself. If your laptop cannot be charged, it will simply not accept the connection.

It is likely that it will realize the device its requesting from is itself and deny the connection based on that assessment alone.

It will be safe to do. In worst case, it will drain the battery slightly faster than usual.

  • What about different ports from different hubs.... to improve performance there's sometimes more than one hub.... i think you're right, though, but I wonder if it would be worth exploring if different hubs might impact the system... as we know, though, USB is a host/client connectivity so, it probably wouldn't have any impact, as you say, they'd handshake be like "I'm a host, you're a host, i can't work with you"... – Kinnectus Jul 9 '19 at 9:55
  • @Kinnectus USB hubs just become devices on the host. It are the host drivers that manage the communication. The only difference will be delay. Basically you get 2 host to client connections simultaneously where the first may or may not succeed, and the second will not succeed for sure. But yeah, it is likely that the PC itself will say: hey, this is from this pc to this pc, lets not do that. Similar how a normal USB-A to USB-A won't work on the same pc. – LPChip Jul 9 '19 at 10:28

The answer depends on whether the ports in question incorporate the necessary sophisticated circuitry which prevents electric surges and on the quality of the USB-C cable.

It is well-known that connecting two computers by a simple USB cable (as opposed to a USB link cable meant to link two computers together), could potentially short out the computer’s power supply for good and possibly cause a fire, depending on the ports and cable.

A cable that is meant to connect computers, a link cable, will have a resistance built-in to stop power surges. For example, see the Belkin Easy Transfer Cable:

enter image description here

If you wish to know what can happen to a USB port to which is plugged the wrong cable, a famous example is what happened to Google engineer Benson Leung, who in the course of testing a USB-C cable destroyed his Chromebook Pixel, and it happened instantly.

So my advice is basically not to do that, unless you are willing to sacrifice your device in the spirit of scientific inquiry.

  • The linked case is definitely not the same case as OP described. They used a 12W charger for iPod. That basically means that the iPod charger and device communicate the acknowledgement and the transfer can begin, but that the cable itself is not capable of handling the full 12W. I argue that the PC will not even give the acknowledgement in the first place and if it does, it will definitely not push 12W over that line. – LPChip Jul 9 '19 at 13:45
  • @LPChip: Any such experiment can only end in two ways: Nothing or Boom. You might be right about some hardware and wrong about others, I can't say which. But I'm not trying it, even if you are right about the chances. – harrymc Jul 9 '19 at 13:53

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