SamyGO

No,AFAIK JTAG placed on DSUB port.
And service port in usb make me thinking that FTTI like RS232 to USB device could be placed on board. If I were you, I connect to service port via USB cable and read USB ID...
That ID will identify the device. I highly believe that Linux will identify connection as /dev/ttyUSB0....
This could also burn your USB port if any trap on that port. Who knows..

You can also use that 3 pin connector (which I believe is RS232 pins.) to reach console too. (It's RS232 on B650's)