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I understand that the COM port is a serial communication port inside a computer.

But in my windows 10 laptop, I don't see any COM port connected.

If I go to the control panel -> Device manager, I see Intel active management technology as a COM port (3).

My questions :

  1. What is the "Intel active management technology as a COM port (3)"?

  2. I have seen some videos, where the Arduino is connected via USB and when we check the device manager, there is a serial COM port of a different number? So, how is this COM port number assigned? And is there a USB to serial conversion (USB to UART) happening inside for this?

  3. On the whole, how many COM ports are there in a normal Windows 10 64-bit computer.

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  • 2. USB can install a comport. (it will be uninstalled when the USB is removed automatically. That's how USB works.) 3. Don't know the exact number, but it can go up to 40 for sure.
    – LPChip
    Commented May 7, 2020 at 9:37
  • 2. When we install a USB, how is the new COM port number assigned? Is it done by the USB or the HOST PC?
    – Freshman
    Commented May 7, 2020 at 9:40
  • Moreover, how do we get so many number of COM ports (as you say around 40), When we don't have that many physical serial ports or USB ports present? Any multiplexing or usage of USB-UART bridge?
    – Freshman
    Commented May 7, 2020 at 9:43
  • both. The USB has an id number, and queries for a free comport to use that one. If you plugin the USB to the same port, you usually get the same comport, but its not a guarantee.
    – LPChip
    Commented May 7, 2020 at 9:43
  • just because you don't have that many ports, doesn't mean windows can't support them. And with USB, virtual comports is an option. With many usb hubs connected to a pc, you can get to 40 comports if you really want to.
    – LPChip
    Commented May 7, 2020 at 9:44

1 Answer 1

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A COM port is simply a serial communications port. It can have a physical external port, or can connect to an internal device to provide a simple interface for software to use.

In your case the COM port connects to a motherboard management interface, in order for a software tool to manage your motherboard firmware.

"Old" COM ports used a UART that was physically connected to the CPU BUS and used memory addresses to communicate with the CPU. These addresses got associated with particular COM ports so that they were consistently given the same port number.

USB is a protocol rather than a CPU addressed device, as such there is no way to know that one device being plugged in is the same as a previous device. As a result the USB device may get a different identifier when plugged into a different socket and as a result Windows will assign it a new COM port.

How many COM ports there are depends entirely on your system. A modern system may have none at all. A system with USB to serial converters could have hundreds. It depends.

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